Crop Rotational Systems

Crawfish may be cultured in two basic crop rotation systems. One is rice-crawfish-rice, and the other is rice-crawfish-fallow/soybean. In both strategies, crawfish culture follows the rice harvest, and the forage crop used for growing crawfish is the crop residue and re-growth of the rice stubble after grain harvest. Advantages of these rotational strategies include efficient use of land, labor and farm equipment. Moreover, some fixed costs and the cost of rice establishment can be amortized over two crops instead of just one.

Rice-crawfish-rice

This approach takes advantage of the seasonality of each crop to obtain two crops in one year. Rice is grown and harvested during the summer, and crawfish are grown during autumn, winter and early spring in the same field each year. (See Table 3.1). As with monocropping systems, crawfish are only stocked initially. They are introduced directly into the rice crop about 4 to 7 weeks post-planting. Following grain harvest, the residual rice crop is usually fertilized with a nitrogen-based fertilizer and irrigated, if necessary, to achieve a ratoon crop (regrowth) of forage (Figure 3.5). Subsequent to the fall “flood-up,” management practices are similar to those of a monocropping system with the exception of a shortened growing and harvesting season to accommodate the establishment of the next rice crop.

A major disadvantage with this rotational strategy is that usually neither crop can be managed to yield maximum production. Rice yields in the South are maximized when rice is planted in early spring. Draining the crawfish pond prematurely to accommodate rice establishment decreases total crawfish yield. Pesticide use is another major management consideration, and it is a particular constraint with this production strategy. Crawfish and rice yields vary and depend on management emphasis. Those systems managed mainly for crawfish can expect crawfish yields similar to well-managed monocropping systems but at the expense of rice yield and vice versa.

Location

Crawfish ponds should be located in flat, open areas, and the soils should have sufficient amounts of clay. Adequate water sources should be available. Clay loams, sandy clay loam and silty clay loams are satisfactory soil types. A clay soil is necessary to hold water and to maintain the integrity of crawfish burrows. Generally, soils that can be rolled into a ball have enough clay for crawfish culture. Elevations must be sufficiently high to allow the pond bottom to remain above water levels in the surrounding drainage ditches and canals (Figure 4.1).

For rice-field ponds, sites are usually limited to existing rice fields. Even so, consideration of which fields will be placed in crawfish production is important. Because of the labor intensive operations of crawfish farming, many rice farmers typically commit only 10 percent to 50 percent of their total rice acreage to crawfish. Often the best producing rice fields are not selected for rotation with crawfish. It is important to select rice fields with adequate all-weather access because crawfish harvesting and pond management are daily activities and often occur during wet weather. Fields selected for crawfish production should have accessible and economical water supplies because the water requirements for crawfish farming are higher than for rice production.

Field size and layout may be an important consideration when producing crawfish on rice acreage. Trapping lanes are more efficient when long and straight, and levee crossings should be kept to a minimum. Limited access for vandals and thieves may be an important consideration. Consideration of the positioning of fields destined for crawfish production may also be important from a pesticide perspective. Positioning of crawfish ponds between producing agronomic fields, or downwind from a field where aerial application of an insecticide is planned is not prudent.

Design and Construction

A number of considerations should be taken into account when constructing permanent crawfish ponds. Many of these also apply to rice fields that are intended for crawfish production. Perimeter levees should have a core trench cleared of debris to prevent water seepage. The minimum perimeter levee base should be 9 feet wide to prevent leakage from the burrowing activities of the crawfish. A levee system 3 feet high is adequate to contain the minimum 8 to 12 inches of water necessary to cultivate crawfish. The land should have no more than a 6-inch fall between perimeter levees. Otherwise, the area should be leveled or divided into two or more ponds. Ponds with steep elevations and resulting depth variations hinder forage establishment, restrict water management techniques and reduce harvesting efficiency.

Wide and deep interior ditches inside crawfish ponds, which are usually adjacent to large perimeter or large baffle levees, should be avoided where possible. These deep areas provide a pathway of least resistance for water flow that can reduce circulation in other areas of the pond, potentially causing poor quality and reduced catch in areas away from the ditches. Additionally, interior ditches are difficult to drain, and they may serve as a refuge for predatory fish after ponds are drained. Interior or baffle levees are constructed to guide water through the pond for proper aeration and to help maintain proper water quality (Figure 4.2).

Baffle levees are built about 6 feet wide at the base. They should extend a minimum of 6 inches above the expected water level for the pond. If the part of the baffle levees above the water line is not substantial enough, settling and erosion will cause the levees to breach in one or two years. Baffle levees should be spaced 150 to 300 feet apart to facilitate water circulation. Core trenches in the baffle levees are not necessary. A recirculation canal outside the perimeter levee and a re-lift pump will aid in water circulation and minimize water discharge (Figures 4.3 and 4.4). Ponds designed to recirculate water are important in areas where the quality of the surface water supply fluctuates or where well water must be pumped from great depths at great cost. (See chapter 6, “Water Quality.”)

Drains should be matched with the pond size, pumping capacity and projected rainfall (Figure 4.5). Two 10-inch drains are sufficient to drain a 20-acre pond. Ponds must allow vehicle access in wet and dry conditions and allow efficient use of harvesting equipment.

Most often, crawfish ponds in a rice-crawfish rotational system use established rice fields where the field lay out and irrigation systems are fixed. Some modifications of the field may be necessary, however, for best results with crawfish. Small levees that are adequate for rice production in shallow waters (less than 5 to 6 inches deep) are not adequate for crawfish production where water levels are usually maintained at 8 to 16 inches. Larger levees are especially critical for the perimeter, which hold in water. Whereas rice production requires a water holding period of 8 to 10 weeks, crawfish ponds are usually flooded for 7 to 10 months. Settling, erosion, burrowing rodents and crawfish burrowing can take their toll on small levees. Therefore, rice fields destined for crawfish production usually require much taller and wider levees. It should be noted though that levee construction/reconstruction should occur before introduction of crawfish brood-stock because levee renovation after crawfish have burrowed can reduce broodstock survival and reproduction.

Levees can also act to keep flood waters out of a crawfish pond at times. Breached levees from flood waters can disperse crawfish out of the pond and introduce unwanted fish into the pond. With electronic laser leveling, some rice fields have become very large with few or no interior levees. If too large, these fields may possess a ratio of linear levee to total pond area that is too large for optimal reproduction, because crawfish use the levees as burrowing sites. Conversely, the presence of too many interior levees potentially provides excess reproduc-

Best Management Practices for Crawfish Pond Construction

A set of best management practices (BMPs) for crawfish production has been developed in cooperation with the USDA Natural Resources Conservation Service (NRCS). (See summary in Table 4.1) These practices seek to minimize erosion, reduce the amount of contaminants (nutrients and pesticides) in effluent discharges and maximize the benefit to wildlife.

STOPPED HERE

Crawfish farming practices are based on annual hydrological cycles and conditions, to which the crawfish have become adapted – namely, seasonal flooding and drying, with the dry period usually occurring during the summer. Pond inundation, or flooding, begins the chain of events that establishes the environment from which crawfish obtain most of their nutrients. As indicated in Chapter 2 under nutrition, crawfish are not routinely fed pelleted rations. Rather, the production strategies in Louisiana and other southern states rely on a forage-based system for providing nourishment to growing crawfish. (Also see supplemental feeding in Chapter 9.)

A forage-based production system benefits crawfish indirectly by supporting a complex ecological community of invertebrates, which the crawfish then consume as high quality food sources. The invertebrate community that is so important to crawfish relies on a continual influx of plant fragments that are in turn consumed by bacteria and other microorganisms. Put simply, the forage crop serves as the fuel for a food web, with crawfish at the top of the food web.

A continual supply of vegetative matter for decomposition is necessary throughout the production season to feed the invertebrate population. This requires a forage crop that yields small portions of its material on a consistent basis over the duration of the season. Too much vegetative input into the system at one time is wasted because it cannot be stockpiled; thus, a large portion deteriorates without being consumed. Also, excess contribution at one time leads to premature depletion of the food resource and can cause low oxygen conditions. Too little vegetative detritus can result in actual food shortages for the organisms that crawfish rely on as high quality food items and, therefore, food shortages for crawfish.

Crawfish farming, as practiced in Louisiana, requires a forage crop that provides plant matter to the underwater food web consistently throughout the growing season. In general, voluntary stands of vegetation perform this task poorly. Terrestrial grasses make for a poor crop because much of the stand is killed upon flooding, negatively affecting water quality and providing short-lived detrital resources (Figure 5.1). Because of the adaptations of rooted aquatic and semi-aquatic plants such as alligatorweed (Alternathera philoxeroides) (Figure 5.2), smart-weed (Polygonium spp.) and others, fragmentation is usually inconsistent and often seasonal. Much of the vegetative biomass of hardy aquatic plants normally remains alive and above water and is unavailable to the food web except for seasonal events such as killing frosts, which often make it available in excess quantities and at times (winter) when it can be least utilized.

Despite the inadequacies of individual plant species in a volunteer stand, the right mixtures of native plants can have a complementary effect and do occasionally produce acceptable crawfish yields. With voluntary stands of vegetation, however, the appropriate mixture of species is very difficult to obtain on a consistent basis. Furthermore, some native plants tend to become so thick they impede harvesting efforts and/or efficiency. Pond warming during spring, and often water circulation, can be slowed by thick stands of plants. Moreover, many voluntary species are considered noxious weeds and are undesirable in fields where agronomic crops will be grown during subsequent years.

Planted agronomic crops routinely have been the most effective forage resources for crawfish ponds. They are effective partly because these plants exhibit the desired characteristics under the long-term flooded condition of a crawfish pond and partly because adequate stands of vegetation are achievable and predictable when recommended management practices are followed.

Rice (Oryza Other Benefits sativa) has become from the Forage Crop the standard forage

crop for the industry Apart from supporting natural (Figure 5.3). Because food production, native and of its semi-aquatic cultivated plants can benefit nature, rice tends to crawfish ponds in other ways.

(1)

Forages provide refuge and crawfish ponds, yet it hiding places for crawfish to furnishes plant fragescape predators and help to ments to the detrital minimize cannibalism. pool in a consistent

(2)

Standing plants provide manner. Sorghum-vertical substrate that allows sudangrass hybrid crawfish to escape the bottom, (Sorghum bicolor utilize the water column and x S. sudanense) is reach the pond surface during also used success-periods of low oxygen. fully (Figure 5.4).

(3)

Forages also provide Millets (browntop, substrate, or attachment Japanese, proso and surfaces, for epiphytic organisms pearl cultivars), grain and invertebrates that comprise sorghum and soybean part of the crawfish's diet. stubble also have been

examined as possible

forage crops, but all these plants demonstrate limited potential for crawfish production when compared to rice or sorghum-sudangrass.

Agronomic plant type and management considerations for maximum yield in crawfish ponds depend on the type of culture system used for growing crawfish. Although basic cultural requirements and practices for producing crawfish are similar regardless of management approach, different production goals dictate different management concerns. This consideration particularly applies to the forage crop and its management. Information regarding recommended practices for planting and management of forage crops can be found in publications such as the Louisiana Rice Production Handbook (Pub. 2321) or by contacting your local LSU AgCenter extension agent.

Monocropping Systems

In crawfish monocropping systems, choice of plant species/ variety and time of planting are the most important considerations regarding forage management. (Also see Management Considerations in Chapter 7.) Aside from relying on voluntary vegetation, choices for maximum benefit are limited mainly to rice or sorghum-sudangrass hybrid, and the choice usually depends on personal preference and logistical considerations. Rice is the most widely used of the two, and variety selection is primarily based on forage characteristics rather than grain traits. Unless waterfowl hunting is part of the overall management goal, grain production in the crawfish forage crop is not desirable.

Until 2004, rice variety selection for use in crawfish ponds had been limited to those varieties developed for grain production. Rice breeders have consistently developed rice varieties for grain production that have high grain-to-forage ratios, are shorter in plant height and are earlier maturing – characteristics that, although desirable for high-yielding grain crops, are less desirable in a crawfish forage crop. Desirable traits for rice used in crawfish ponds include high forage biomass production, low-temperature tolerance, longer maturity cycle, high resistance to lodging, slow senescence (breakdown) rate, disease resistance and propensity for plant re-growth in spring.

In 2004, the LSU AgCenter released the first rice cultivar developed specifically for use in crawfish monocropping systems. “Ecrevisse” was the culmination of years of screening and evaluation of rice genotypes originating around the world, and selection of one line that was further improved (purified) under Louisiana's growing conditions. This new variety exhibits much greater forage biomass production, better persistence under the extended flood conditions of a crawfish pond and has a greater propensity for post-winter regrowth than the commonly used domestic varieties (Figure 5.5). Because of the selection criteria used and the methods employed for further development of this variety, there was an inherent selectivity for disease resistance and adaptability to South Louisiana's soil and environmental conditions. Therefore, until a better variety is found, this new variety should be the hands-down choice for establishing a rice forage crop in crawfish monoculture ponds in Louisiana. Ecrevisse is almost certainly limited to crawfish monocropping systems, however, because it is a short grain rice and exhibits poor milling traits, making it less desirable for use in grain markets.

Selection of rice varieties other than Ecrevisse for establishment in crawfish monocropping ponds is currently limited to commercially available high grain-yielding varieties. Recommendations from commercially available varieties are scant because few comparative studies have been made regarding their suitability in crawfish ponds. New varieties are released and adapted so often that it is impractical to investigate thoroughly each one within the different regions where crawfish are grown. In general, those varieties that are well-adapted to local conditions, are taller, have a longer maturity cycle, tiller well, produce abundant forage biomass and senesce slowly are likely to be the best choices for planting in crawfish ponds. In theory, supported only by preliminary research, it may be beneficial to mix several varieties when planting in crawfish ponds. Differences in post-flood characteristics of different varieties, such as fragmentation rate, crop persistence and re-growth potential may provide detrital material to the pond on a more consistent and extended basis than a forage crop composed of only a single variety.

It has also been demonstrated that sorghum-sudangrass, commonly used by cattlemen for grazing and hay, is a well suited alternative forage crop for crawfish monocropping systems. It grows rapidly, can produce nearly twice the amount of forage biomass as rice, is very hardy and drought resistant and may prove more reliable in some cases than rice when a stand must be established in late summer. This crop, if managed properly, also exhibits good persistence in crawfish ponds with consistent fragmentation of material well into the season. One of the main benefits of sorghum-sudangrass over rice is that it does not require as much moisture for optimum growth. An adequate rice crop can rarely be achieved without some irrigation during the summer growing phase in Louisiana. Conversely, sorghumsudangrass may need little or no irrigation and, in fact, cannot tolerate saturated soils for an extended period while in its early growth stages. Another potential benefit of sorghum-sudangrass over rice is that it has a later recommended planting date. Because of its rapid growth potential, when the optimal window for rice establishment has passed, forage stands can often still be established (or salvaged) by planting sorghum-sudangrass.

Regardless of which agronomic crop is chosen for use in crawfish monocropping systems, time of planting is extremely important. For best results, when waterfowl hunting is not a consideration, it is essential to plant early enough in the summer to achieve maximum vegetative growth, but not so early that the plant reaches full physiological maturity. A forage crop that matures or “fills grain” prior to the onset of winter tends to senesce more rapidly (Figure 5.6), often resulting in early depletion of the forage resource and subsequent stunting before the crawfish season's end. In South Louisiana, the most appropriate planting time for rice for crawfish forage is during the first two weeks of August. For sorghum-sudangrass, optimum planting time is generally in the last two weeks of August.

Recommended

planting dates

tend to be earlier

Rotational Cropping Systems

Multicropping of rice and crawfish requires different forage management strategies than monocropping systems. Different crop types are not an option, because crawfish always follows a rice (for grain) crop. (Also see Management Considerations in Chapter 7). Rice variety selection is limited under this production strategy because of the grain production requirements. Rice varieties are generally chosen for their grain-yielding and milling characteristics rather than forage characteristics, which tend to be inconsistent with those traits needed for high density crawfish production. Under moderate densities of crawfish, however, many high grain-yielding rice varieties are sufficient. For maximum benefit under high population densities, rice variety selection in a multi-cropping strategy should also take into consideration the ratooning characteristics of the variety. Residual straw and stalks in harvested rice provide little long-term benefits in terms of food resources. The bulk of the required forage base is derived mainly from ratoon or re-growth of the rice stubble after grain harvest.

Within the confines of best yielding (and milling) rice varieties, consideration should also be given to those varieties with a high propensity for ratoon forage production (Figure 5.8). Commercial rice varieties are constantly changing as new and improved lines are released; therefore, variety selection should be based on the best available information, which is usually obtained from LSU AgCenter extension personnel or publications such as “Rice Varieties and Management Tips” (Pub.2270), published annually by the LSU AgCenter Louisiana Cooperative Extension Service.

Management of the forage crop for crawfish under a rotational strategy is principally related to ensuring proper re-growth from the ratoon crop and minimizing the negative effects on water quality from breakdown of straw and debris from the grain harvest. As with crawfish monocropping systems, fertilization and irrigation is often needed to ensure maximum forage production. Because of previous applications of phosphorus and potassium in the main rice crop, subsequent applications may not be necessary, but often additional applications of nitrogen are required for maximum response and re-growth. Soil tests and/or advice from a professional should aid in determining exact nutrient amendments needed for each situation.

Rice stubble responds best to applications of fertilizer, followed by irrigation, shortly after grain harvest. Extended delays in supplying moisture to the stubble during dry conditions can result in poor re-growth. Also, periodic irrigation or, as with crawfish monocropping, maintaining a shallow flood may be warranted to ensure adequate moisture and uptake of nitrogen applications. Water quality will deteriorate quickly, however, with a constant flood due to high amounts of decomposing plant matter and must be improved before crawfish begin to emerge. Improved quality can be accomplished by water discharge or allowing for complete evaporation, followed by refilling, often several times. Since most rotational cropping occurs in precision-leveled fields, the most efficient means of water and forage management prior to establishment of the permanent flood is to implement a shallow flood (2-4 inches deep) and allow for evaporation, with water replenishment before the soil becomes too dry.

To further minimize water quality concerns, the straw and debris left from grain harvesting operations can be baled and removed, burned or chopped (to speed degradation). Those practices should occur during or immediately following grain harvest and before applying fertilizer and water. Timely rain or irrigation is essential for proper re-growth and also aids in partial decomposition of dead plant material that can cause water quality problems upon flooding for crawfish. Nonetheless, timing of the permanent flood should be delayed in these systems until cool weather persists. This is usually early to mid-October or later in South Louisiana. As with crawfish monocropping systems, weed-free fields are not necessary for adequate crawfish yields, and caution should be exercised anytime pesticide applications are contemplated.

Post-Flood Management of the Forage Crop

Regardless of the production strategy employed or forage type used, few forage management options are available, or needed, following crawfish pond flood-up. For ease of harvesting, some producers choose to establish trapping lanes in the forage crop prior to flood-up. Lanes can be established by mowing, disking or dragging a heavy object in a path where boat “runs.” Other farmers elect to establish lanes, if needed, after flooding by repeated trips with a harvest boat. For best results, trapping lanes should be constructed so that traps rest squarely on the bottom to optimize catch efficiency.

Forage biomass persistence, especially with rice, can sometimes be improved by minimizing flood depths. In general, with the exception of some aquatic plants, the deeper the water depth is maintained in ponds, the more rapidly the forage crop will

be depleted. Forages also can become depleted prematurely when crawfish biomass is high or when the crop matures and forms grain prior to winter. Grain formation, aside from coinciding with increased breakdown rates, often attracts birds that, in high numbers, may physically break down the forage crop prematurely.

Rice crops, especially immature stands, may have a tendency to resume growth when temperatures warm sufficiently in the spring, provided living stalks survive the winter and crawfish density is not exceedingly high. This new growth can be critical in providing additional food resources at a time when they are needed the most. To encourage spring re-growth, however, pond managers may need to lower the water level in turbid waters to expose viable nodes on the rice stalk to warmth and sunlight. Lowering water level is an important, but often overlooked, management strat-

Crawfish aquaculture relies on natural reproduction of resident or stocked adults to populate the ponds. Yields of harvestable animals within a season depend on broodstock survival, successful reproduction and survival of offspring. In established ponds, however, where production occurs in the same location each year, crawfish populations are usually self-sustaining with no need for supplemental stockings, short of some major catastrophe that interrupts the normal life cycle, such as a major die-off (from pesticides or other contaminates) prior to successful burrowing. Once a pond is established, subsequent crawfish crops rely on holdover broodstock from a previous cycle. This reliance is possible because harvesting operations are inefficient, allowing significant “carry over” of unharvested individuals from year to year, even under the most intensive harvesting efforts.

Since crawfish populations tend to be self-sustaining, stocking is usually only needed in new ponds, when a pond has been idle for a season or longer or after extensive levee renovation or other events that disrupt the reproductive process in permanent ponds. Stocking of new ponds is usually necessary, unless it is known beforehand that sufficient numbers of crawfish of the right species are present to serve as broodstock. When a pond is idle for at least a season and remains dry for much of that time, crawfish broodstock mortality may increase and/or reproductive processes may be hampered to the point that restocking is needed.

Restocking is often needed following major levee renovation because the most productive broodstock are usually burrowed into the levees in open ponds, and earth moving will often destroy broodstock within their burrows or prevent reemergence in the fall. Sometimes repair or renovation of existing levees is unavoidable, but if done on a large scale during the interval between crawfish burrowing in spring or early summer and reproduction during the fall, restocking will likely be needed. Unfortunately, restocking may not always be possible before the next production season. Severe drought conditions during the critical reproductive period (July to October in the South) also can impair reproduction.

Field rotational methods for crawfish aquaculture do not normally allow for crawfish populations to reach high densi-ties. To ensure adequate numbers of broodstock in a pond that has been out of production for one or more seasons, rotational ponds are usually stocked annually. (Also see Chapter 3.) For the most part, population control is one of the most difficult aspects of crawfish production due to, in part, factors that are not under the producer's control. Many factors associated with stocking practices, however, do fall under the control of a pond manager and can greatly influence production outcomes during the subsequent season. Research has indicated that broodstock survival and reproductive success following stocking can be highly variable, though many of the reasons are still unidentified.

Species and Size

Producers in Louisiana should stock only red swamp crawfish because of their high fecundity and preference in the marketplace. In areas with no marketing concerns over white river crawfish, some mixture of reds and whites is acceptable. Size of mature broodstock is of little concern because, although larger crawfish produce a higher number of young, fewer crawfish are purchased per pound of broodstock. Smaller crawfish produce fewer young on average, but more crawfish are purchased per pound. Therefore, total recruitment potential is similar regardless of the size of the broodstock used. Yet, smaller crawfish are sometimes sought because their price per pound is usually lower. Some anecdotal evidence suggests that small, mature broodstock may be hardier than very large adults, but this has yet to be verified.

Dates

New ponds in a monocropping system are usually stocked between April and July when broodstock sources contain a high percentage of sexually mature individuals with at least some advanced ovarian development. (See Chapter 3.) Cost of broodstock is sometimes an important variable when decisions to stock are made, with prices usually lowest near the end of the harvest season. Stocking should follow all major levee work, most notably when levees provide the only exposed ground in a flooded pond. Crop rotational systems that employ the field rotation approach are usually stocked in late May, in June or July, when rice plants are large enough to withstand the crawfish without damage and when most needs for harmful pesticide applications have passed – about 45 days post-planting.

Habitat

Crawfish broodstock are obtained from a variety of habitats (monoculture ponds, rotational ponds and the wild crawfish fishery) and from a wide array of conditions within each of those habitats. Research has not shown a strong link between habitats broodstock may be collected from (say, farmed versus wild) and their survival or reproductive success. It is likely, though, that the environmental conditions within habitats where breeding stock is obtained, such as water temperature, quality and quantity of nutritional resources, crowding and other factors are responsible for much of the variability in reproductive success. Suitable broodstock can be obtained from any type of pond or natural habitat as long as the crawfish are in good health and not under undue stress. Common stressors in any habitat are related to elevated temperatures, low oxygen, poor nutrition and overcrowding, including overcrowding inside traps prior to harvest.

Vegetative cover within the pond being stocked plays an important role in broodstock survival. Although daily nutritional needs are easily met after stocking (because of low densities of crawfish stocked), vegetative cover serves to protect stockers from predators and cannibalism and may serve to buffer the pond temperature. Many types of vegetation also provide access to the surface in times of low oxygen. Vegetation, or some other form of cover, along the water's edge also provides protection from predators while brood crawfish are constructing burrows. If levee surfaces are completely bare and devoid of cover, artificial cover, such as cardboard, plywood, clumps of hay or corrugated roofing material strategically placed along the perimeter near the water's edge will enhance successful burrowing.

Pond water temperature during and after stocking can also be a critical factor. Crawfish cannot tolerate water temperatures over 92 F to 95 F for long periods. Crawfish may seek deep or shaded areas of the pond, if available, to avoid the extreme temperature of midday, but if refuges are unavailable, crawfish will simply leave the pond or die. Increased water depth, vegetative cover and shade, or water exchanges are all options for buffering the effects of high water temperatures at stocking.

Handling

Proper handling of broodstock is also critical for best results. Care should be taken to limit the amount of time brood-stock remain in the trap prior to harvest and in storage and transit after harvest. Lengthy exposure to elevated temperatures, direct sunlight or wind will kill or severely stress broodstock, as will rough handling or contamination with foreign substances such as fuel or chemicals (Figure 6.1). Crawfish should be kept clean, moist and at temperatures between 60 F and 80 F. These practices are best accomplished by shading (with tarps, burlap or other suitable materials) and wetting sacks of crawfish periodically. Broodstock should not be kept in refrigerated coolers or completely iced down. Limited use of ice, however, may be a suitable means of controlling temperature and moisture during transport. Harvesting or transporting crawfish broodstock at dawn, dusk or night is also a suitable means of reducing stress. Always exercise caution when handling the animals. Excessive or rough handling can lead to crushing or cracking of the delicate exoskeleton, raising mortality.

Conditions under which crawfish are introduced to the pond are also critical. Contrary to rumor, crawfish should always be emptied directly into the water and not onto dry ground adjacent to the water (Figure 6.2). Because crawfish are mobile, there is no need to equally disperse them over the entire pond or even around the entire perimeter, but some dispersal may be necessary in large fields. However, crawfish should be stocked into each section or segment of a divided pond. Best results are achieved when water temperatures do not differ greatly from the temperature of the crawfish themselves at the time of stocking. Therefore, stocking during the cooler hours of the day/night or during cloudy/rainy weather is one way to minimize this difference and maximize survival.

Rates

Stocking rates are based primarily on anecdotal evidence, pertinent factors affecting successful survival and burrowing and, to some extent, personal preference. Recommended stocking rates vary depending on the number of native crawfish present and the amount of cover around and within the pond. Amount and type of cover, such as vegetation in the pond and at the water's edge often will affect the number of crawfish surviving and successfully burrowing after stocking. Stocking rates of 50 lb/ac to 60 lb/ac are recommended for areas lacking native crawfish and with sufficient cover to protect stocked crawfish from predators (both in the pond and while burrowing).

Stocking rates may be decreased from these general recommendations when healthy populations of native crawfish are present. Similarly, they should be increased when conditions make for poor survival following stocking or when burrowing is hazardous due to predators or inclement weather. Although not well documented, it is possible that effective stocking rates may be lowered somewhat when stocking occurs in ponds with permanent levees that already have many old or existing burrows.

In very large ponds with flat bottoms and few interior levees, effective stocking rates may be limited by the amount of linear levee surface around the pond. When the ratio of pond surface area becomes exceedingly large compared to linear levee, available burrowing area at the water's edge may be limited, thereby necessitating lower stocking rates. Simply put, not enough levee is available for crawfish to burrow into.

Anticipated weather patterns after stocking also may influence desired stocking rates. Successful burrowing depends on critical moisture levels in the soil. Drought makes for poor burrowing by lowering water levels and drying out the levees. Frequent rainfall helps stabilize water levels and makes burrowing easier for the crawfish, possibly even allowing burrow excavation away from the water's edge. In short, stocking recommendations of 50 lb/ac to 60 lb/ac are only general recommendations – many producers elect to stock up to 80 lb/ac or more when post-stocking survival is unpredictable. Producers should weigh all of the factors in their given situation and adjust stocking rates accordingly.

Sex Ratio and Condition of Broodstock

The sex ratio and condition of crawfish broodstock both are important. At least 50 percent of the crawfish used as stockers should be females (Figure 6.3). The percentage of females can be higher, but percentage of males should not be higher than females. Healthy males can mate with more than one female. Quality crawfish broodstock also should have an outwardly healthy appearance and be highly active at normal temperatures.

Under typical stocking conditions, most of the broodstock should be sexually mature, especially if environmental conditions in the new ponds are poor (little food or shelter, poor water quality, high temperatures, etc.) or the pond must be drained soon after stocking. If pond conditions or water levels deteriorate soon after stocking, it is desirable that crawfish be able to begin burrowing shortly after introduction. The goal of broodstock management is for crawfish to start burrowing on their own (for reproductive purposes) when they have reached maturity and mated, rather than being forced to burrow for survival purposes because of pond drainage. Therefore, under less than ideal conditions, it is desirable to stock crawfish that are nearly all mature at the time of stocking.

Conversely, if new ponds have optimal temperatures and oxygen levels, contain sufficient cover to minimize predation and can maintain these conditions for an extended period after stocking, it may be desirable to stock with younger crawfish that are not closely synchronized in their state of maturity. Under favorable conditions, “pre-adult” crawfish can mature and mate in the new pond following stocking, and a mixture of younger and more mature crawfish at stocking might extend the effective spawning period over more months in the subsequent production season. An increased spawning period increases chances of successful reproduction and recruitment under unpredictable conditions before and after flooding, such as drought, hurricanes, delayed flood-up or other events that might interfere with normal recruitment. Nonetheless, for the most predictable results, at least half of the crawfish at stocking should be sexually mature.

In addition, when stocking occurs during summer, at least some portion of the mature females should show signs of ovarian development. Mature females possess yellowish to tan, or even darker eggs (see Figure 2.4 in Chapter 2). The optimal percentages of crawfish with advanced ovarian development and the optimal stages of development at stocking have not been determined and probably vary from situation to situation.

As with any species, reproduction calls for nutritional needs beyond those required for body maintenance or even growth. Crawfish need to have enough stored energy reserves prior to burrowing not only for survival during the long burrow confinement, but also for the reproductive processes that occur in the burrow, where additional food resources are limited or nonexistent. Crawfish used for broodstock should possess adequate nutritional reserves prior to stocking or be able to acquire what is needed following stocking but prior to burrowing. Hence, aside from exhibiting signs of egg development, suitable stocker crawfish also should possess signs of adequate energy reserves in the hepatopancreas (or “fat”), the main energy storage organ (Figure 6.4). The hepatopancreas of dissected crawfish should appear full and fatty and golden or yellow, but not brown, green or watery looking, which indicates poor nutrition and body condition. Examination of a few dissected individuals from each population of crawfish stocked is the preferred way to estimate body condition and reproductive stage.

Preliminary evidence suggest that, in some cases, supplemental feeding of ponds prior to harvesting crawfish for brood-stock may improve body condition and increase the reproductive performance of the stockers. Predictable, cost effective feeding protocols, however, have not yet been developed. Furthermore, given an adequate period from stocking to burrowing of several or more weeks in a new pond or rice field, crawfish may be able to gain sufficient energy reserves in the relatively food-rich environment without the use of supplemental feeds.

Figure 6.4. A full, fatty and bright yellow or orange hepatopancreas (digestive gland) inside the body of a mature female prior to burrowing indicates the much needed energy reserves for reproduction (left), whereas a small, watery, amber hepatopancreas indicates a less desirable body condition (right). Note, the dark eggs in the ovary of the crawfish on the left – indicating advanced reproductive development.

Post-stocking Recommendations

To achieve maximum results, stocked crawfish must survive and, if necessary, complete maturity, increase their energy reserves, mate and then burrow successfully. Therefore, environmental conditions in the pond should be maintained to support this process for the maximum number of stockers. This means water temperature and oxygen should remain within acceptable ranges, and water levels should remain relatively constant. Water replacement and/or flushing may be necessary. To provide crawfish every opportunity to burrow successfully and in optimal conditions, water should remain on the field as long as possible, or feasible, after stocking.

Premature draining can prevent some crawfish from reaching the desired state of maturity and/or condition, and also can make burrowing more difficult or impossible. Fluctuating water levels, especially in the absence of timely rains, also can hinder proper burrowing. Unchecked predators, especially fish and birds, can significantly reduce numbers of broodstock, and extensive levee work following burrowing can further reduce survival, reproduction and recruitment. Therefore, attention given to ponds after stocking is as important as other factors relating to the practice of stocking brood crawfish in new or idle ponds.

Stocking Guidelines

• New or idle crawfish ponds should be stocked with approximately 50 to 60 pounds of crawfish per acre.
• Add more if pond (or crawfish) conditions are questionable, and less if crawfish are already present.
• Stock healthy crawfish (sacrificed individuals generally have bright yellow fat).
• Be sure at least 50% are female.
• Be sure at least 50% of females are mature (sacrificed individuals will have yellow to brown eggs).
• Don't be concerned about individual size, or origin of stock, as long as the crawfish are mature and healthy.
• Red swamp crawfish only, from more than one source, is preferred.
• Stocking over several days is preferred.
• Do not use crawfish that were stored in a cooler.
• May to June is the preferred time to stock, although stocking in July may be possible under the proper conditions.
• Move crawfish as fast as possible to the pond; keep wet and shaded.
• Stock all sections of the pond and place crawfish directly in the water, not on dry ground.
• Do not drain fields for at least 2 or 3 weeks after stocking.

Summary

To ensure maximum benefits and achieve the most return for dollars spent while minimizing risks, care should be taken to optimize a stocking strategy. Receiving ponds should be completed and readied for animals in advance of stocking with adherence to recommendations for water quality, cover and predator control. All, or in some cases, most of the crawfish to be stocked should be red swamp crawfish, and the stocking rate should be carefully determined based on all applicable factors, including personal experiences for a particular geographical location and habitat. To prevent the proverbial “all the eggs in the same basket” syndrome, consider stocking any given pond on more than one date within an acceptable time frame and with crawfish from more than one source. Furthermore, mixing females with varying maturity/egg stages, depending on when ponds are stocked and the length of time ponds will remain flooded after stocking, will aid in expanding effective spawning dates and lessen potential setbacks from unforeseen circumstances.

Stocking should be done with healthy animals of the proper ratio of females possessing a high level of energy reserves and proper handling during and after harvest. If possible, stocking should accompany rainy weather and/or occur when pond temperatures are the lowest in the day. Pond levels should remain mostly constant, at near normal depths, until a week or so before draining, when water level can be dropped substantially and held at that level until final draining to trigger last-minute burrowing. Ponds should remain flooded for as long as possible or practical following stocking. Lastly, hold levee disturbances during summer to a minimum. The initial stocking of brood crawfish is one of the least costly components of farming crawfish. Any attempt to “save” money by purchasing poor quality broodstock or failure to follow recommended stocking protocols will invariability be very expensive to the producer if reproductive failure is the result.

Poor water quality that persists for days and weeks is detrimental to crawfish production. Water quality is influenced by many factors, both environmental and biological. Some environmental conditions such as temperature and rainfall are beyond the control of the farmer. Other factors, such as the type of vegetation planted for crawfish in summer, when the vegetation is planted, how the vegetation is managed prior to flooding the ponds and when the pond is flooded will influence water quality in crawfish ponds. Most serious water quality problems occur in the fall, usually in the first two to six weeks after ponds are flooded and later in the early spring when pond water warms. All crawfish farmers will have water quality problems at some point during the production season, but the magnitude and severity is dramatically reduced at the outset by insuring ponds are properly designed, securing a stable and reliable water source, by matching the pumping capacity with production acreage, managing vegetation prior to flooding ponds in the fall and water after flooding and taking corrective management steps when water analysis tests indicate action is necessary.

Water Supply and Quantity Required

Both surface and subsurface water is acceptable for crawfish farming. Wells provide predator-free water, but they have a limited discharge capacity and higher investment and pumping costs. Because well water contains no oxygen and is usually high in soluble iron and toxic hydrogen sulfide, the water must be aerated to add oxygen and remove iron and sulfide prior to entering the pond (Figure 7.1). Surface water is satisfactory if it is pollution-free and if nuisance predatory fish are screened out. Although cheaper to pump, surface water is usually not as reliable in quantity and quality (Figure 7.2).

Pumps, motors and pipes must be matched to obtain the most efficient performance. Lift should be minimized as much as possible to reduce pumping costs. Pond location and local energy costs dictate the type of pump and power source best used for crawfish ponds. Surface water contains predatory fish that should be removed through a 1/2-inch mesh aeration screen (Figure 7.3). Smaller fish passing through the 1/2-inch mesh aeration screen usually don't pose a serious predation problem to young crawfish. These fish are killed when the pond is drained in the summer. If pools or puddles containing fish persist in the pond bottom during the summer, it is important that the puddles be dried or treated with a fish toxicant prior to filling the pond in the fall to prevent contamination of the pond with predatory fish.

A pumping capacity of 75 to 100 gallons per minute per surface acre is ideal for intensive management strategies for crawfish ponds that average 14 to 18 inches deep when fully flooded. This pumping rate is sufficient to exchange all the water in the pond over four to five days. Complete water exchange may be required in the early fall when water is flooded onto vegetation. Warm weather leads to rapid plant decay and high demand for oxygen. When the water is depleted of oxygen for long periods, significant crawfish mortality or stress that reduces growth can occur. Ponds can be designed to circulate water and maintain satisfactory oxygen levels, thereby reducing pumping and water management cost (see Design and Construction in Chapter 4). Replacing bad water in the pond with fresh, oxygenated water helps maintain satisfactory water quality. It is more effective to drain a portion of water from the pond and then pump oxygenated water to replace it than it is to drain and pump at the same time. By draining some of the water first and then re-filling, oxygenated water will be distributed through the entire pond. On the other hand, when draining and filling at the same time, many areas of the pond may not be properly flushed of bad water. Exchanging water in crawfish ponds to improve water quality is energy intensive and expensive, and decisions to do so should be based on the results from routine monitoring of water quality, especially oxygen content.

In reality, few crawfish farmers in Louisiana supply 75 to

100 gallons per minute of water per surface acre to crawfish ponds. The following managewater supply is not acreage. By filling flood-up, a pump acre will provide sufficient capacity ample, if the pond it can be initially filled to 7 to 9 inches as opposed to 14 to 18 inches. Not only will there be less water to replace during low oxygen episodes, but less vegetation is submerged and oxygen demand is reduced. When temperatures have sufficiently cooled in winter, usually below 65 F, and oxygen demand is reduced, additional water can be added to bring the pond to full depth. One possible disadvantage of the shallow flood is that females with young burrowed near the top of the perimeter levee may not exit the burrow if rainfall in the fall and winter is limited. If the water supply is much less than 30 gallons per minute per surface acre, options for effectively managing water for optimal crawfish production are limited.

Water Quality

Water quality depends on management and on properly designed and constructed ponds that have a dependable water supply. Important water quality variables are dissolved oxygen, pH, total hardness, total alkalinity, iron, hydrogen sulfide content, ammonia, nitrite and salinity (salt content).

Dissolved oxygen is the most important and low oxygen may be responsible for the death of more crawfish in ponds, either directly or indirectly, than any other factor. Temperature has a major effect on oxygen levels in ponds (Figure 7.4). Warm water cannot hold as much oxygen as cold water. Also, rising water temperature increases biological activity, so oxygen is consumed at a faster rate. When the water temperature increases from 70 F to 80 F, the rate of oxygen loss caused by decomposition doubles. Potential problems with insufficient oxygen can be expected whenever water temperature exceeds 70 F. During warm periods, ponds with an inadequate pumping capacity and excessive amounts of decaying vegetation will suffer from severe oxygen depletion, which can slow crawfish growth and reduce production if the condition is allowed to persist.

Crawfish are generally tolerant of low oxygen, but persistent exposure to extremely low oxygen for weeks can reduce production. The first two to six weeks after the initial flood-up is the most critical time for juvenile crawfish. Ideally, dissolved oxygen should be maintained above 2 parts per million (ppm) for good crawfish production but this content can be difficult, if not impossible, to sustain in the warmer months. When oxygen levels remain consistently below 1 ppm throughout the day for several weeks, crawfish become sufficiently stressed that they may cease feeding. Growth will slow and catch may significantly drop until oxygen levels increase. When oxygen levels remain below 0.5 ppm throughout the day for a week or more, newly hatched juveniles and molting crawfish may die. Larger crawfish stressed by low dissolved oxygen climb to the surface on vegetation or traps and expose their gills to higher oxygen levels at the surface (Figure 7.5). This behavior is usually not visually observed with juvenile crawfish because of their small size. The shelf life of live harvested crawfish in the cooler is reduced considerably if they have been exposed to low oxygen in ponds prior to harvest.

Because of high pumping costs, water management deci

sions should be based on oxygen measurements. No benefit to crawfish health and survival is gained by exchanging water if oxygen levels are satisfactory. Although pond water lacking in oxygen is often clear and dark (the color of tea, coffee or cola) and may have a smell of hydrogen sulfide (“rotten egg” odor), one should not rely on visual observation or smell to determine oxygen concentration. Dissolved oxygen can be checked several different ways. Dissolved oxygen meters are best if you have many ponds

to check (Figure 7.6). Most producers, however, choose oxygen

test kits because the kits are relatively inexpensive and simple to operate. The easiest kit uses a vacuum ampule that draws in a water sample. The value is determined by matching the color of the sample to a chart.

Oxygen deficiency is corrected by replacing or exchanging pond water with fresh, oxygenated water or by circulating and aerating existing water in the pond. Mechanical aerators, though not commonly used in the crawfish industry, are effective in aerating water in the vicinity of the aerator but are mostly ineffective in larger ponds with dense stands of vegetation because oxygen can not effectively be distributed throughout the pond. Installation of an aeration tower is recommended to oxygenate well water or surface water prior to it entering the pond. The aeration tower, if constructed properly, also will remove large predatory fish when using surface water. Pumping water through an aeration tower divides the water into small droplets (Figure 7.7). This technique gives maximum oxygen transfer to the water droplets. Properly designed aeration towers will add 1 to 2 pounds of oxygen to the water per horsepower

hour. Well water is also aerated to some extent when it is exposed to the atmosphere as the water travels through flume ditches.

The source water pH after being aerated should range from 6.5 to 8.5, and both total hardness and total alkalinity should range from 50 ppm to 250 ppm as calcium carbonate. As a general rule, most waters and soils used for crawfish production in Louisiana are sufficiently high in hardness and alkalinity and do not require additions of agricultural limestone other than what may be required for the forage crop being cultivated. If the pH, hardness and alkalinity are low, incorporate agricultural limestone into the pond bottom during the next dry cycle. The amount of agricultural limestone required must be determined from a soil test analysis and the kind of forage crop to be grown during the summer. Water and soil samples can be analyzed by the LSU AgCenter's Soil Testing and Plant Analysis Laboratory for a nominal fee, and recommendations will be provided as to the suitability of the water and soil for crawfish production with the results of the analysis. Contact your local LSU AgCenter

also to avoid expenses associated with unnecessary pumping.

water and soil samples for analysis.

Dissolved iron and hydrogen sulfide are toxic to crawfish at concentrations often found in well water, but the two compounds are lowered to nonharmful concentrations when the water is oxygenated (Figure 7.8). Where iron and hydrogen sulfide concentrations are high, it may be necessary to place a flume ditch or pond between the well and the crawfish pond to allow the iron to settle out before entering the pond. Non-ionized ammonia and nitrite are toxic to crawfish at concentrations exceeding 2 ppm and 5 ppm (as nitrogen), respectively. Concentrations this high are not likely to occur in crawfish ponds because the crawfish production intensity is low and ammonia is rapidly taken up by aquatic plants present in the pond.

As mentioned in Chapter 5, extreme care must be taken with pesticides in or around crawfish ponds. Only a few agricultural chemicals are labeled for use in crawfish ponds. Crawfish are very sensitive to various classes of pesticides, particularly insecticides, which can be toxic even at low concentrations. Because crawfish are often grown in rotation with other agricultural crops, such as rice, or near agricultural crops where pesticides are used, extreme caution should be taken to insure crawfish are not exposed to pesticides, particularly after the pond or field is flooded and crawfish have already emerged from their burrows. Be sure that your neighbors and aerial applicators are aware that you are farming crawfish nearby. Read and follow label instructions of any chemicals or compounds before using it in or near crawfish ponds. The toxicity of many agricultural pesticides on aquatic organisms, including crawfish, can be found in Southern Regional Aquaculture Center Fact Sheet 4600 “Toxicities of Agricultural Pesticides to Selected Aquatic Organisms,” which can be downloaded from the Southern Regional Aquaculture Center Web site. Contact your local LSU AgCenter county extension agent or other knowledgeable professionals when questions about pest problems arise or about the use any pesticides.

Although crawfish are fairly tolerant to salt water, areas subject to saltwater intrusion are not recommended for crawfish production. Tolerance to salinity is directly proportional to crawfish size. Newly hatched young die at 15 parts per thousand (ppt), and juveniles die at 30 ppt if kept in this salinity for a week. Salinity affects crawfish reproduction at much lower concentrations, and the effect of continuous exposure to low salinity on crawfish reproduction is not fully known. Ideally, crawfish ponds should not be located where salinities higher than 3 ppt are likely to occur through most of the crawfish production season. Coastal areas with low salinity water usually have highly organic soils that are not idea for pond construction or for maintaining adequate levels of oxygen throughout the crawfish growing season. The salinity of the source water should be less than 1 ppt if rice or sorghum sudangrass is the desired forage crop. Crawfish farmers in coastal regions should monitor tidal influenced surface waters for salt content particularly during a drought.

Management Considerations

Flooding date is important in water management. Flooding is usually timed to coincide with peak spawning and juvenile recruitment in September and October. For this reason, it is seldom beneficial to flood ponds to full depth before mid-September. If ponds are flooded too early, extreme heat could seriously deplete the water of oxygen, causing significant crawfish mortality if left unmanaged. Several inches of water can be held in ponds planted with rice in early August to suppress weed growth without serious harm to crawfish. Ideally, sustained air temperatures should be in the low to mid-80s in the afternoon and low to mid-60s in the morning before beginning fall flood up, and this is usually early October in southern Louisiana. If ponds are large and pumping capacity is low, or if large amounts of dead plant material are present, delaying flooding until late October or early November when temperatures are lower is usually better. On occasion, heavy rainfall associated with tropical depressions or hurricanes will dump several inches of water on crawfish ponds in late August and early September. Although holding this water to reduce pumping costs is tempting, because of the extreme heat at that time of the year, releasing this water is usually best even if some juvenile crawfish are present. Early rain, however, can usually be safely held at manageable depths on rice forage planted in early August (“green rice”).

The type of forage and how the forage is managed prior to flood-up affects water quality. (See monocropping and rotational cropping systems in Chapter 5). Best water quality is maintained in ponds with rice planted in early to mid-August solely as crawfish forage because the oxygen demand of green, actively growing rice is low. Rice-crawfish rotation ponds with large amounts of rice stubble and straw following rice harvest are likely to have serious oxygen problems after fall flood-up unless the straw is baled and removed, burned or chopped and irrigated to speed breakdown and reduce oxygen demand. Significant problems with low dissolved oxygen also can occur in ponds with a dense stand of sorghum-sudangrass because of the high amount of vegetation produced and inability to control other grasses in the pond that have a high oxygen demand. Ponds that are not planted and have large amounts of volunteer grasses usually have severe oxygen depletions soon after flood-up because grasses decompose quickly. Ponds with large amounts of aquatic plants, like alligatorweed, usually have fewer oxygen problems but alligatorweed alone is not a desirable food for crawfish (Figure 7.9).

Crawfish do not have the ability to congregate in high numbers around an oxygen source for short periods of time during low oxygen episodes as do fish. Therefore, aerated water must be transported through the pond to reach all the crawfish to achieve maximum survival, growth and yield. As stated in the Water Supply and Quantity Required section in this chapter, it is important to match pumps and transport systems (pipes, canals or ditches) to maximize energy efficiency and water distribution. Water can be guided through the pond with small internal baffle levees to direct the flow of water throughout most areas of the pond and reduce areas with stagnant or “dead” water unsuitable for crawfish. Ponds can be designed to recirculate and aerate water to maintain water quality using return ditches and re-lift pumps (Figure 7.10). Recirculating water is often less expensive than flushing ponds and has the added benefit of reducing impact of releasing low oxygen water on the environment.

Best Management Practices

In addition to providing a highly valued and desirable seafood product, crawfish ponds serve as favorable wetland habitat to many species of waterfowl, wading birds and furbearers. Often, land that is marginal for traditional row crops is used in crawfish production. Integration of crawfish aquaculture with traditional agricultural land uses serves as a practical means of land and water conservation. Voluntary best management practices (BMPs) are an effective and practical means for conserving water and protecting the environment. Effluent or “tailwater” is discharged when rainfall exceeds pond storage capacity, when ponds are flushed to improve water quality and when drained at the end of the production season. Crawfish effluent water is usually low in nutrients and oxygen demand, but turbidity and suspended solids can be high at certain times of the year. The following set of BMPs have been identified that will minimize potential impact of crawfish pond tailwater (effluent) on the environment.

1. Capture and store rainfall to reduce effluent volume and pumping costs (Figure 7.11). Allowing the normal pond level to fall at least 4 inches below the level of the standpipe (or more, depending on the season and pond design) from normal evaporation without re-filling will greatly reduce the volume of water leaving ponds during rainfall events by increasing the storage capacity of the pond to accumulate rainfall. Drain pipes within ponds can be painted a bright color to indicate the target water depth at which pumping is needed. An added benefit of this practice is the reduced need for pumping well water to maintain ponds at or near maximum depths.
2. Install drain outlets to draw overflow from the pond surface. Water from the lower layers of a pond is generally of poorer quality than that near the surface. This difference can be especially true in terms of suspended solids, oxygen demand and nutrients. Pond drains should be constructed to allow water to leave the pond from the surface, not the bottom (Figure 7.12). Existing drains that draw from the pond bottom and

incorporate external structures to regulate pond depth should be modified during regularly scheduled pond renovations, to draw water from near the pond surface.

1. Reduce pumping costs and improve flushing efficiency. When flushing crawfish ponds in the fall to improve water quality, avoid pumping and draining at the same time. Fill the pond to one-half to two-thirds of its maximum storage capacity at initial flood-up. To flush the pond, open the drains and allow the entire pond to drop to a depth of roughly one-fourth of storage capacity, then re-fill the pond with fresh water, again to no more than one-half to two-thirds of maximum storage capacity. This type of flushing ensures that stale water will be diluted with fresh water throughout the entire pond, preventing the establishment of “dead” areas where water will not normally flow with conventional flushing. Additionally, less water is used and released to the environment by not flooding the pond to maximum depth with the initial flood-up. The pond can be filled to maximum depth (storage capacity) in late November when temperatures have dropped sufficiently. Alternatively, baffle levees can be used to direct water flow through the pond to eliminate low oxygen areas. In areas where the quality of surface water is occasionally unacceptable or where well water must be pumped from great depths, water recirculation can be a cost-effective alternative.
2. Minimize sediment loading when draining. Harvesting activity, wind and waves and crawfish foraging actions cause turbidity, or muddy water (Figure 7.13). Although this condition can be alleviated somewhat in crawfish-only ponds by postponing draining until most of the crawfish present have burrowed in the early summer, it poses problems in ponds where draining must be accomplished much earlier to allow for a commercial rice or other crop to be planted. In these instances, no specific recommendations have been formulated to reduce suspended sediments in ponds or tailwater, but suspending harvest activities for 1-2 weeks prior to draining may improve water clarity prior to discharge. The use of vegetated filter strips and channel vegetation (vegetated drainage ditches) also will probably be beneficial in improving water clarity because heavy sediments settle out and are trapped as water velocity is reduced as it passes through the vegetation (Figure 7.14 ). Other approaches, such as maintaining in-pond buffer zones of natural aquatic vegetation like alligatorweed, reduce the level of suspended sediments in water caused by disturbance of the pond bottom from wind and wave action and erosion of pond levees.

5. Practice water detention during summer drawdown. A majority of suspended solids and nutrients are discharged from crawfish ponds in the remaining 10 percent to 20 percent of the pond water. Retaining water several days prior to complete draining or allowing the remaining water to evaporate if the production practice will allow for this can significantly reduce nutrient loads in tailwater because many nutrients are bound to particles of sediment, which can settle out of the water column prior to discharge (Figure 7.15).

1. Reuse pond water. To save on pumping costs, conserve groundwater and reduce tailwater discharge, if possible; pond water can be pumped into adjacent ponds or reservoirs and then reused. Transfer can usually be accomplished with a low-lift pump, and water can be replaced later by siphon. In some circumstances, it may be possible to drain water directly into ponds with lower elevations.
2. Use tailwater for irrigation. Under some conditions, pond water discharge can be used to irrigate crops. Most crawfish aquaculture in Louisiana occurs in areas used for rice agriculture, and crawfish ponds are frequently adjacent or in close proximity to rice crops. Tailwater discharged in spring and summer into drainage ditches can be re-lifted or, in some

cases, directly used to irrigate and replenish water in rice fields, which are planted in mid-March through April (Figure 7.16). Under some circumstances, diverting pond discharge can result in excessive erosion, so care must be taken when considering this practice.

1. Use natural or constructed wetlands and sedimentation ditches to reduce tailwater solids and nutrients. Natural wetlands are an effective means of treating aquaculture effluents, but care must be taken not to overload these systems. The presence of established stands of aquatic plants in spring and summer in ponds with volunteer vegetation increases nutrient uptake and reduces the level of suspended sediments in water caused by disturbance of the pond bottom from wind and wave action and erosion of pond levees. Although dense stands of volunteer aquatic plants are usually considered problematic in commercial crawfish operations, establishing manageable stands or strips of aquatic plants, such as alligatorweed, inside ponds, even when using cultivated forages such as rice or sorghum-sudangrass, may help to improve effluent quality as well as provide cover and food when other forages have become depleted. Drainage ditches, particularly those with a slight gradient and containing emergent aquatic plants, can effectively function as settling basin for heavier solids. Sediments that accumulate in drainage ditches over time and hinder drainage can be removed in some cases and used to rebuild levees (Figure 7.17).
2. Practice erosion control in drained ponds. When ponds are drained and idle, especially in winter in Louisiana, substantial erosion of the exposed pond bottom can occur, affecting both the serviceability of the pond and the receiving

pipe. For this reason, drains should always be closed if possible when ponds sit empty, and ponds should be partially or completely refilled as quickly as possible.

10. Minimize environmental impacts during pond renovation. Use sediment from within the pond to rebuild levees and fill in low areas (Figure 7.18). Do not remove it from the pond unless absolutely necessary. During renovation, drains should be kept closed to minimize erosion and discharge of sediment. Levee height usually can be increased at this time to allow more management flexibility in capturing and storing rainfall or water from surrounding ponds. In this way, effluents also will be further reduced.

waters on the outside of the drain

and filling low areas.

The low-intensity production technology used in farming crawfish requires a harvest method unlike those used to harvest fish. A passive system is used, employing baited traps beginning as early as November and continuing through the following April-June. If fall and winter production of juveniles is low, or where crawfish are grown in northern portions of the state, initiation of harvest seldom begins before March and is often extended into late July.

Crawfish recruitment is continual over much of the 7- to 10-month growing season. Regular, frequent harvests are necessary, in contrast to the infrequent batch harvest with seines common with fish culture operations. Harvesting crawfish with seines or trawls is typically not feasible because of dense vegetation. Crawfish may be harvested with traps from well-managed ponds 40 to 90 days per year. In Louisiana, two-thirds of the crop is generally harvested from March through June, when densities of marketable crawfish are highest and crawfish are most active. Trapping is labor intensive, and over half of all production expenses are associated with harvest. Bait and labor are typically the major harvesting costs. Efficient harvesting is essential for crawfish farming profitability.

Factors Influencing Catch and Harvest Size

Crawfish catch from production ponds can vary two- or three-fold from day to day (Figure 8.1) and is influenced by many factors. Water temperature and density of marketable crawfish are the primary factors that govern seasonal changes in crawfish catch. However, water quality, type and quantity of vegetative forage, weather, lunar phase, as well as crawfish reproduction, growth and molting patterns all play significant roles in the variation observed in daily catch. A summary of the major factors affecting crawfish catch is outlined in Table 8.1.

Size at harvest is largely influenced by environmental conditions – much more so than genetic factors. Crowding reduces growth and usually leads to stunting. Crawfish are aggressive and territorial. Larger crawfish intimidate and out-compete smaller individuals, thereby suppressing growth. To ensure growth of smaller size classes and achieve high yields, crawfish should be harvested soon after attaining acceptable marketable size. Harvesting removes larger individuals from the population, reducing aggression and leaving space and food resources for undersized animals.

The minimum acceptable size for crawfish for consumption varies with season, abundance and price; however, consumer preference is typically for 23 individuals (“count”) per pound and larger (3 1/2 inches and longer). Large crawfish, 10- to 15-count per pound, usually command premium prices.

Traps

During the early history of crawfish farming, many styles and sizes of traps were used by crawfish farmers, and all caught crawfish with varying degrees of efficiency. Presently, the “pyramid trap,” with three entrance funnels has become the industry standard (Figure 8.2). For years, most traps were made from 3/4-inch mesh, plastic-coated hexagonal-shaped (hex) poultry wire (19 or 20 gauge). These mesh-sizes typically retained crawfish of minimum marketable size, about 3 inches and longer (35 count per pound). Although hex wire traps dominated the industry prior to 2003, today most traps are made from 3/4-inch or 7/8-inch welded square mesh wire. Traps made of square mesh wire are more durable. Traps made from square mesh wire also retain smaller crawfish than comparable size hex-mesh wire. Research by the LSU AgCenter has shown that 3/4-inch square wire will catch on average about one-third more crawfish than 3/4-inch hex wire traps with an overnight set. The catch with 7/8-inch square mesh traps is roughly equivalent to that of 3/4-inch hex mesh traps.

Pyramid traps are constructed from wire formed into a three-sided, three-dimensional form shaped like a pyramid. Optional cylindrical vertical extensions, usually 6 inches long, are often added to increase the height of the trap for use in deeper water (see Figure 8.2). A 6-inch diameter plastic pipe (or extruded collar) is placed at the top of the trap to function as a handle and prevent crawfish escape through the open top. Traps made from 24-inch wide by 44-inch long to 24-inch wide by 54-inch long wire are the most prevalent sizes. Final overall dimensions of the traps are approximately 17 inches wide at the base and, with a 6-inch extension, about 26 inches tall.

The inside diameter of entrance funnels is usually 1 3/4 to 2 inches. Since wind and wave action and avian predators (herons and egrets) that perch on the plastic collars can cause traps to topple, metal supporting rods (5/16-inch diameter) are often added to minimize toppling. Crawfish traps do not have bait protection containers (bait wells) as is often found in crab traps because catch is usually substantially reduced with their use.

Baits

Bait, which is required to attract crawfish into traps, is the single highest expense in crawfish production and accounts for nearly one-third of production costs. Bait cost depends on the type, amount used per trap, trap density and trapping frequency. Two types of bait commonly used are natural fish baits and formulated baits.

Fish baits are usually sold frozen in 80-pound or 100pound boxes. Clupeid or “sardine-like” fishes, specifically gizzard shad and Gulf menhaden or “pogy” (Figure 8.3) are the most widely used natural baits in Louisiana where commercial fisheries exist for both species. Common carp, buffalofish, herring (“slicker”), suckers and catfish are also used. Shad, menhaden and carp are superior to other natural fish baits as attractants. Beef pancreas (“beef melt”) commonly used by recreational trappers, is an effective attractant but too expensive for commercial use. When a shortage of bait occurs in the Louisiana bait fisheries, significant quantities are shipped in from other states.

Formulated crawfish baits, often referred to as “artificial” or “manufactured” baits, were commercialized in the early 1980s and are produced by several feed companies, both within and outside of Louisiana. These cylindrical pellets consist mainly of cereal grains, grain by-products, commercial flavoring agents and a binder. They are generally one-half to 2 inches in diameter and 1 1/2 to 3 inches long and sold in 50-pound bags.

Fish baits are seasonal in supply and price and more expensive than formulated baits. Large farms may have freezers or coolers for storage, but smaller farms require daily deliveries. Labor is needed to cut the fish to puncture the swimbladder so it will sink and to portion it into efficient sizes, which further adds to its cost. Formulated baits do not require refrigeration and are easier to handle. Some companies offer different formulations for use in cool or warm water.

Baiting Strategies

Significant cost reductions can be achieved by employing efficient baiting strategies. The main considerations are selection of bait type relative to season and quantity of bait used per trap. Shad and menhaden are more effective attractants than formulated baits at water temperatures below 70 F (Figure 8.4), and, in Louisiana, fish baits are used almost exclusively during winter and early spring trapping (November through March). Even though fish baits are more expensive, the average two- to three-fold increase in catch over formulated baits under these conditions compensates for the additional bait cost. When water temperature exceeds 70 F to 75 F and ponds become depleted in forage (corresponding to late March to early April in South Louisiana), formulated baits become equally effective or more effective than fish baits, and they are the most cost-effective attractants. At water temperatures of 65 F to 75 F, a combination of fish and formulated bait added to traps in approximately equal portions can increase catch as much as one-third over fish alone or formulated bait alone; however, the logistical inconvenience of handling two baits at the same time in harvesting boats must be considered when employing this strategy.

During winter, when crawfish feeding activity is minimal and the number of harvestable crawfish is still relatively low, studies suggest that one-fourth pound of bait per trap is sufficient to harvest available crawfish. When waters warm in the spring and the crop of harvestable crawfish nears maximum levels, the quantity of bait should be increased to about one-third pound per trap. Although it is not practical to portion bait into each trap carefully, farmers can gauge and monitor bait use by keeping good records on the total quantity used for the number of traps in a pond or the farming operation. For example, when using one-third pound of bait per trap per day, a 100-pound box of fish bait should be sufficient to bait 300 traps. If only 200 traps are baited, too much bait is being used. A 50-pound bag of formulated bait is sufficient to bait 150 traps. The trapper should pay attention to the amount of bait remaining in the trap after a 24- or 48-hour soak (set time). If significant bait residue remains in the trap the amount can be reduced somewhat. If bait is rapidly consumed, however, consideration can be given to increasing the amount of bait. Fresh bait should be used each trapping day, especially with fish baits. To maximize crawfish movement to freshly baited traps, bait residue should not be disposed of in the pond.

Trapping Strategies

Traps are placed in rows to facilitate harvesting by boat (Figure 8.5). Distance between traps depends on trap density (Table 8.2) and a spacing of 40 to 60 feet between individual traps and between rows is most common. Where annual yields of harvestable crawfish are expected to exceed 1,000 pounds per acre, a trap density of 18 to 22 square-mesh pyramid traps per acre, baited and emptied three to four days per week is recommended. It is not uncommon for farmers to use a lower trap density of 10 to 15 per acre if a low-standing crop of crawfish is present or if large areas are to be trapped and labor is limited. Trap density should be increased by two to three traps per acre if hex-mesh pyramid traps are used. If buyers require daily delivery of crawfish, or the price is high and catch justifies the effort, crawfish can be harvested five to six days per week,

Table 8.2. Spacing between rows (in feet) and the distance between traps (in feet) to obtain a specified number of traps per acre.

Distance Distance Traps Between Traps Between Rows Per Acre 40 4027 40 5022 40 6018 40 7215 50 4022 50 5017 50 6015 60 4018 60 5015 60 6012 66 6610

but the average size of crawfish and catch per trap will usually decrease after a few days. If multiple ponds are present on the farming operation, harvesting activities can be rotated among production ponds.

Normally, traps are emptied 24 or 48 hours after baiting. The 48-hour soak time is generally employed in late fall and winter when crawfish activity is slow and standing crop of harvestable crawfish is low. Typically, it is best to harvest three or four consecutive days per week with several days rest between trapping episodes when crawfish are abundant and active.

Following nonharvest days, unbaited traps need not be lifted from the water and emptied prior to baiting because no additional yield is obtained by removing these crawfish (often referred to as “walk-ins”) prior to baiting. To some extent the average size of crawfish caught is correlated with the time traps remain in the water. The shorter the trap set, the higher the number of small crawfish caught. After the bait has been consumed, or the attractants in the bait have dissipated, some crawfish are able to escape through the entrance funnels, and escape is easier for the smaller animals. After several days of intense trapping, the average size of crawfish decreases and the catch often declines as larger animals are removed and the standing crop of market-size crawfish decreases.

Insufficient harvesting in ponds with dense crops of crawfish hastens forage depletion and increases aggression among animals, resulting in growth suppression and stunting. Ultimately, yields and profitability can be greatly reduced. Conversely, excessive trapping may reduce harvest size by removing crawfish before they have had sufficient time to grow to larger sizes, and harvest efficiency is decreased in this way. Because of the basic inefficiency in current trapping methods and gear, there is no evidence to indicate crawfish can be over-harvested. The more farmers monitor and understand the structure of their populations, the better equipped they can be to make decisions regarding harvest intensity.

Occasionally, harvesting schedules Crawfish Harvest

and strategies must Recommendations at a Glance be adjusted to accommodate markets.

Three-funnel pyramid trap, 3/4-

Buyers may prefer inch or 7/8-inch square wire to have the product delivered only on

18-22 traps/acre in high-density certain days, such as ponds, (typically permanent Thursday through monocropping ponds)

Sunday, when demand is usually

10-15 traps/acre in low-density

highest. Addition-ponds, (typically rice-crawfish ally, market demand field rotations) for crawfish early in the season may

Trap 3-4 days/week

allow for various sizes of crawfish to

24-hr or 48-hr trap soak time

be sold with little problem, but when

40-90 trapping days per season

supplies are more abundant, trapping

Use fish baits below 70°F,

strategies may need formulated baits above 70°F to be adjusted to maximize crawfish sizes, even at the expense of overall yield. As markets evolve and conditions change, maximizing profits in crawfish production no longer automatically means maximizing yields. Planning and good communication with potential buyers early in the season can allow trapping strategies to be developed that respond to market preferences and improve a producer's competitive position.

Harvesting Machinery

Methods used to empty traps vary within the industry. Producers with ponds less than a few acres in size rarely use motorized boats because of the added expense. Traps may be emptied by harvesters who walk shallow-water ponds while

pulling or pushing a small boat. One person can empty about 400 traps per day. Other trappers use small, flat-bottom boats propelled by push-pole or paddle, but this method is no more efficient than walking.

In larger ponds, a boat propelled with an engine and drive mechanism adapted for use in shallow water is the most efficient harvesting equipment. One approach used widely in the crawfish industry is the Go-Devil^® or similar designs, with 8- to 18hp air-cooled engines or larger and long shafts with weedless propellers (Figure 8.6). The boats have flat bottoms, are made from aluminum and are typically 14 to 16 feet long by 4 to 6

feet wide. It is common forthese boats to travel down trap lanes with fishermen emptying and re-baiting each trap from one side of the boat without stopping. The first trap is lifted, dumped and re-baited in the time it takes to reach the next trap. The freshly baited trap is set beside the next trap, and the process continues throughout the pond. A boat powered in this manner generally requires two persons, one to empty and re-bait the traps, and a second to steer. As many as 300 traps per hour can be emptied and re-baited.

Many crawfish producers prefer to use a rig designed specifically for harvesting crawfish (Figure 8.7). This boat uses a 12- to 24-hp air-cooled engine that operates a hydraulic pump and motor to propel a metal wheel attached to the boat. Metal cleats are welded to the wheel, which is mounted either to the front to pull the boat forward, or to the rear to push the boat in shallow water. The wheel's hydraulic steering can be operated with foot pedals, leaving the driver's hands free to empty and re-bait traps. A single person can handle about 150 to 200 traps per hour. Up to 300 traps per hour can be emptied and baited with two persons. Rigs with the hydraulic wheels mounted in the rear are preferred whenever boats must cross levees, either within or between ponds. Some hydraulic-propelled boats are also equipped with side-mounted rubber wheels to allow travel down farm roads for short distances.

Boats are equipped with sacking tables to consolidate harvested crawfish. Trap contents are emptied onto

the sacking table, which usually has two to six loose mesh “vegetable” sacks temporarily attached. Each sack can hold 3545 pounds of crawfish depending on how tightly the harvester packs them before changing sacks. Bait residue and other debris remain on the table to be discarded while crawfish drop into the hanging sacks. Producers are increasingly using in-boat graders to cull submarketable animals while still in the pond (Figure 8.8). Larger crawfish remain on the grader and are sacked. Smaller crawfish are usually returned to the pond but this may not be advisable in many situations (see Managing Harvest, Chapter 9).

Pond Flood-up

Crawfish are confined to the burrow until the hard plug that seals the burrow is sufficiently softened by external moisture. (See Chapter 2). Pond flooding, especially when associated with heavy rainfall, facilitates and encourages the emergence of crawfish from burrows. Brood females emerge with young (and sometimes eggs) attached to the abdomen, and hatchlings are quickly separated from the females to become independent. Because reproduction is somewhat synchronized in pond-reared crawfish, ponds are routinely flooded in autumn to coincide with the main period of recruitment. Continuous recruitment and differential growth often results in a population of mixed sizes, especially in monocropping situations (Figure 9.1). Typically, spawning in burrows, hatching (either in burrows or ponds) and emergence of females from burrows all take place more or less continuously from September through November. As a result, sufficient young-of-the-year crawfish are usually available throughout this time period to produce the season's crop.

Timing of fall flooding is particularly critical in crawfish farming. The goal is to time flooding to provide the best habitat for young-of-the-year recruitment, and the most fundamental factor relating to the timing of flooding involves water temperature. Warmer water is more conducive to faster growth of crawfish. The warmer water is, however, the less oxygen it can hold. At the same time, the warmer the water is in a newly flooded field, the more rapidly oxygen will be consumed in the breakdown of vegetation. Unless extremely high amounts of water are available for daily exchanges, early flooding almost always results in depressed oxygen levels. This situation is aggravated if most of the vegetation is already dead or begins breaking down rapidly upon flooding. This occurrence can significantly reduce survival and growth of any early emerging crawfish and reduces profitability through increased pumping costs and reduced yields (because of poor utilization of forage and reduced crawfish recruitment). Therefore, timing of pond flood-up should reconcile water quality issues with optimal crawfish growth opportunities associated with warm weather.

Flooding also must be timed to coincide with the development of the forage crop, whether it be rice, sorghum-sudangrass or volunteer vegetation. If terrestrial vegetation is flooded too early, growth may be curtailed, and the breakdown process may be accelerated. In cooler waters, even poor quality forage will persist longer, and the slower breakdown process generally results in more nutrition for the crawfish crop.

It is important to remember that ponds need not be fully flooded during the 1- to 2-month period when brood crawfish and their young emerge from their burrows. In some situations, young-of-the-year crawfish can successfully begin growing in as little as 4 to 6 inches of water, especially if abundant green vegetation provides cover. During the period following initial flooding, maintaining good water quality and high oxygen levels is more important than filling the pond to its full depth.

Population Management

Despite some efforts to limit farmed crawfish populations only to the red swamp crawfish, excluding the white river crawfish from ponds whenever possible, both species are responsive to routine culture practices and often coexist in production ponds. In general, these two species have environmental requirements that are conducive to the low input aquaculture systems used in Louisiana and surrounding states, and they are frequently found in the same water body. Though the abundance of one species may vary among and within culture ponds from year to year, red swamp crawfish most often dominate and are the desired species in the marketplace. It has been hypothesized that the abundance of red swamp crawfish is linked to their greater reproductive potential because growth and survival do not differ greatly between the two species. Other factors also may be involved. In some cases, white river crawfish increase in abundance as the culture pond ages and can become the dominant species over time.

It also has been speculated that ponds flooded in November, rather than in September or October (in Louisiana), may favor the white river species because later flooding dates better coincide with the timing of reproduction for that species. Research has shown that the species of crawfish that enters the pond first in greatest numbers after fall flood-up has the best likelihood of dominating the population. Thus, if red swamp crawfish become established first after the pond is flooded, they will dominate the population and later harvest. If juvenile white river crawfish become established before red swamp crawfish juveniles enter the population, white river crawfish will dominate the population and subsequent catch.

Currently, no reliable management recommendation is made for ridding a pond of white river crawfish once they have become established. If the problem with white river crawfish is so severe that it interferes with a farmer's ability to market the catch, a few management options can been considered, but it must emphasized these recommendations are not known to be reliable nor have they met with predictable success. They include (1) draining a pond quickly in March or April before white river crawfish mature and burrow in large numbers, followed by re-stocking the pond with red crawfish; (2) flooding a pond in September to allow red swamp crawfish hatchlings to emerge before white crawfish. Extra caution must be taken to manage water quality associated with September flooding; (3) if the crawfish farming operation is large enough, taking a pond out of production for 1 or 2 years to kill most of the resident crawfish, followed by restocking with red swamp crawfish can be tried.

Management of a crawfish population after flood-up is complicated by the inability of producers to assess the population accurately. Because of continual recruitment and difficulties in sampling, crawfish producers have little knowledge of the density and structure of the crawfish population in their ponds. Sampling is crude and accomplished by dip net sweeps and baited traps (Figure 9.2). Population management entails little more than controlling timing of the flood to coincide with normal reproduction peaks, ensuring adequate water quality and food resources and adequate harvesting pressure to remove market size animals. Reducing densities to control overpopulation in ponds has shown promise in limited research but has not yet become a common practice. Supplemental stocking in underpopulated ponds within a production season sometimes occurs but may not always be feasible.

Supplemental Feeding

As described in the forage section of this manual (Chapter 5), crawfish production in the southern United States relies almost solely on established forage crops for providing nourishment to growing crawfish. Feeding of prepared feeds is not a common practice as it is in shrimp farming or most fish farming enterprises. Rather, crawfish receive their sustenance from sources within a complex food web, similar to that which occurs in natural habitats. The natural food chain, at times, may be inadequate to sustain maximum crawfish production, especially when forages become depleted or when adequate forage crops are not established. It is also likely that, as crawfish density increases beyond some optimum density, natural food resources become depleted. Under these conditions, production of highly nutritious invertebrates, important components of the crawfish's diet, may be lacking, resulting in poor crawfish growth or, worse, stunting at submarketable sizes.

Feeding or supplementing natural food resources has been tried by some producers to increase crawfish production. Farmers have provided hay in place of, or in addition to, growing vegetation. Hay has been added either at the beginning of the season prior to flood-up or later in the season after the depletion of standing vegetation. Large round bales or numerous smaller square bales have been placed in ponds, often marginally distributed within the ponds, with bales either left intact or broken up to some degree. Conventional thinking at the time was that hay would undergo decomposition similar to forage crops to furnish the needed “fuel” for the food chain. Positive results, in terms of more or larger crawfish harvested, were usually nondetectable and often the practice resulted in deterioration of water quality.

Lack of (or poor) results from hay supplements was due to the fact that the hay did not function as plant fragments from standing forage crops would. First, the distribution of hay, even if bales were well dispersed in the pond, usually only covered a small fraction of the entire surface area of the pond. This restriction was not conducive to maximum benefit because crawfish, and their prey, are well scattered throughout the pond and commonly do not congregate to feed. Second, decomposing plant material is most nutritious for a relatively short period (days to weeks, depending on water temperature), so anything less than regular offerings of fresh hay, well-dispersed over the entire pond area, does not meet the nutritional needs of the organisms in a pond over the course of a season. Furthermore, large amounts of decomposing hay are wasted because it cannot be fully utilized by the target organisms and can lead to oxygen depletion, either locally surrounding the bale or over the entire pond.

Various agricultural byproducts, such as manures, sweet potato and sugarcane products have been evaluated as supplemental feeds for crawfish production, but most have provided no noticeable or only marginal results and are considered nonpractical. The problems arise more from practical aspects of handling, frequency requirements of feeding and distribution over the pond, rather than strictly nutritional limitations.

Feeding of formulated, pelleted feeds, much like those used in catfish culture, have been tried in a number of commercial and experimental crawfish ponds over the years. Positive results were inconsistent and difficult to measure, and feeding practices frequently proved uneconomical even when a positive biological response was observed. Although some carefully controlled studies showed a positive response of crawfish to supplemental feed additions, results were variable and unpredictable. Some studies reported no increase in average yield or harvest size after feeding. Others reported significant increases in yield; however, yield increases were mostly from an increase in the harvests of smaller, low-valued crawfish.

Supplemental feeding studies under simulated pond conditions in outdoor tanks or in a laboratory setting with high densities of crawfish consistently demonstrated the limitations of forage-based culture systems and usually yielded more, or larger, crawfish. Yet, repeatedly, responses from supplemental feeding in ponds were marginal and

unpredictable at Broodstock Feeding best and proved disadvantageous at One objective that may justify times. It was found the use of supplemental feeds in that feeding while crawfish culture, short of increasharvesting could ac-ing overall yield or harvest size, tually result in lower is to increase body condition and yields – possibly be-energy reserves of broodstock. cause of satiation of Recent research, although limited crawfish appetites or and preliminary, has indicated that interference with the crawfish survival and reporduction attractant from the within the burrow during sum-bait in traps, result-mer/fall may be better in females ing in lower catches. with the greatest energy reserves. Feeding immedi-Feeding practices may be better ately after the last applied toward animals to be used day of harvest each for broodstock, rather than for week, when using growing crawfish for harvest.

an intermittent harvesting schedule of three to four consecutive days per week followed by a three- or four-day reprieve from harvesting lessened the chance of reduced yields when feeding but did not always eliminate it. (Also see Managing Harvest below).

In short, there are probably times when the food chain associated with a forage crop is limited and nutritional supplementation may be needed to sustain maximum production. Aside from concerns with feeding and harvesting, however, other constraints that currently limit the economic use of supplemental feeds include knowing when feed is needed, how much to feed, how often to feed, specifically what nutrients are limited and when feeding will predictably produce positive results. If most of the crawfish population has reached or is nearing sexual maturity (even at a small size), further growth is limited, even with ample food. Therefore, much of the benefits of supplemental feeding will not be realized. Furthermore, it is difficult to obtain an accurate assessment of crawfish populations, and, based on research, it has been determined that supplemental feeds offered to highly overcrowded crawfish populations may be only marginally effective at increasing average size or yield. Therefore, without the ability to accurately assess situations in a pond and counter with cost-effective feeding practices that will yield positive results on a consistent and predictable basis, no dependable recommendations exist for use of supplemental feeds in forage-based crawfish ponds.

Feeding expensive feeds, formulated to meet all the nutritional requirements of the cultured animal (as in catfish production), may not be the most cost-effective means of supplementing the nutritional needs of crawfish. Since forage-based systems inherently furnish much of the required nutrition for growing crawfish, low-cost, incomplete feeds used as true supplements to the natural food web may provide the most cost-effective alternative. Because of the intermittent feeding nature of crawfish and the presence of other invertebrates, much of the dispensed feed will cycle through the food web to be utilized indirectly by crawfish. Therefore, supplemental feeding must be viewed as “feeding the total system” and not just the crawfish. Based on what is known about crawfish ponds, it is likely that protein and/or energy are the primary limiting factors when natural foods become scarce. Therefore, single feedstuffs high in energy or protein may provide adequate nutritional supplementation at a fraction of the cost of expensive, formulated “complete” feeds containing vitamins, minerals and other expensive nutrients.

Certain agricultural grains and seeds may be appropriate supplemental feeds for crawfish raised in ponds containing some natural foods. Agricultural seed crops are usually high in protein and/or energy, are routinely available in crawfish farming regions, are easy to apply and are usually a fraction of the cost of high protein formulated feeds. Damaged (broken) or low-grade products are often available at reduced prices. Rice grains and whole soybeans, among other grains, have been investigated as supplements to crawfish with encouraging results in highly controlled conditions. When repeatedly evaluated under realistic field conditions, however, similar problems existed with harvesting, timing, assessments and predictability, as with the use of pelleted feeds. Nonetheless, research is continuing to investigate strategies whereby supplemental feeds might be used to effectively augment the forage-based system and increase economic returns in a more reliable manner. As of yet, no feeding recommendation is available for increasing production or average harvest size in forage-based systems on a predictable and feasible basis.

Some research has been directed at the use of feeds in “off-season” or “year-round” nonforage-based crawfish ponds. Under that scenario, feeds are intended to furnish nearly all of the nutritional needs of growing crawfish – much like intensified catfish operations. Although experimental results were encouraging, no large commercial operation has yet employed this type of production system. Moreover, because of the increased cost of producing crawfish in such a system, the breakeven price is increased dramatically, making it more suitable for crawfish culture outside of Louisiana near prime out-of-state markets.

Although in high-density permanent monocropping ponds low reproduction efficiency may be offset by large numbers of crawfish, this balance is usually not the case in new or rotational ponds requiring stocking. Since a limited number of brood crawfish are initially stocked in first year ponds, reproductive condition is important. Crawfish broodstock are often obtained from densely populated ponds and at a time when food availability is at its lowest, so improvement in reproductive condition through short-term feeding prior to capture of broodstock may improve survival and reproductive success after stocking, especially if new ponds will be drained soon after crawfish are stocked. Little research has been completed with regard to this objective for feeding, but an active research program is underway to determine the merits of such short-term feeding practices and to establish some possible guidelines.

Managing for Larger Crawfish

Diseases

Serious disease problems associated with nonintensive crawfish culture are thought to be rare. Individual crawfish are known to be susceptible to various pathogens, such as bacteria, virus, fungi, protozoans and parasites; however, epidemic outbreaks sufficient to affect commercial production in earthen ponds have not been demonstrated. Significant disease problems are more likely to be encountered in intensive, high-density holding systems, such as purging and soft-shell production facilities. One study reported that of 15 outbreaks of bacterial septicemia (Vibrio mimicus and V. cholera) diagnosed in Louisiana crawfish, four cases were from ponds and 11 were from high-density holding systems. Diseases are most likely to occur during periods of elevated temperatures and/or periods of oxygen stress.

All North American crawfish are suspected vectors of the Aphanomyces fungi, or plaque fungus, that was notorious for eliminating many populations of native European crawfish in numerous lakes, rivers and streams. Although carriers, North American crawfish, including those cultured in the South, are not normally affected by the fungus. Procambarid crawfishes are sometimes affected by other agents that do not necessarily have an effect on production but may hinder crawfish marketability because of certain physical effects. Microsporida can infest the abdominal muscle, giving it an unattractive milky-white appearance (porcelain disease), and various ectocommensal organisms that attach to the exoskeleton can limit the acceptability of crawfish if the infestation is heavy. These conditions are not usually common and have little economic impact, although at times buyers may refuse to accept lots of crawfish with heavily soiled exoskeletons.

Because of the insignificance of known diseases in pond culture of crawfish, disease management is not deliberate. Practices that prevent food shortages, overcrowding and low oxygen (common stressors) are the extent of practices related to disease management in the crawfish industry.

Predators

Crawfish are, however, susceptible to any number of predators that thrive in and about the shallow, vegetated waters of crawfish ponds. Predaceous aquatic insects consume young, recently molted crawfish. Bullfrogs, amphiumas (a large eel-like salamander) and several species of water snakes flourish in crawfish ponds and readily consume all sizes of crawfish (Figure 9.5). Various turtles and the occasional alligator will

Figure 9.5. Apart from humans, many wildlife species have a taste for crawfish.

prey on crawfish. Small mammals, such as the Norway rat, mink, raccoon, opossum and otter are often abundant and will consume crawfish and sometimes the bait placed in crawfish traps. Raccoons and otters also will damage traps when getting to the crawfish and/or bait. Although collectively these predators can consume large quantities of crawfish, crawfish reproduction and growth rates are usually sufficient to prevent major harvest losses.

Even though predatory fish, if not controlled, can be the most significant predator encountered in crawfish ponds, avian predators, especially carnivorous wading birds, are perceived by many producers to cause the most harm. Fish are easily controlled, though often difficult to eliminate from ponds if they become established (Figure 9.6). Fish are controlled by thoroughly drying pond bottoms during the interval between

seasons or by treating standing pools of water with a fish toxicant, followed by proper screening of incoming water. Some fish manage to enter ponds by swimming up drain structures or on the feet, feathers or fur of other animals visiting the ponds. If not controlled, fish will consume large quantities of crawfish and/or compete with crawfish for the natural food items that crawfish rely on.

Avian predators are not as easy to control as fish. Many bird species consume crawfish, and, except for allowable hunting seasons for certain waterfowl, nearly all piscivorous (fisheating) birds are federally protected (Figure 9.7). Although the actual impact on operational costs and production is not known, many producers perceive bird depredation as a significant and growing problem. Carnivorous waterbirds find crawfish ponds to be food-rich havens, and these ponds often offer water and food resources when they are in short supply in natural habitats. Some researchers have provided convincing evidence of a direct relationship between the increase in colonial wading bird numbers from the 1960s to 1980s and the increase in crawfish pond acreage in Louisiana during that period. Anecdotal evidence also suggests that some noncrawfish-eating species have recently adapted their feeding habits to take advantage of the plentiful supply of crawfish from aquaculture ponds. Effective control measures are lacking, and the size and shape of most commercial crawfish ponds prevent the economical use of netting or other exclosures.

Nuisance Wildlife

Note: These recommendations are in accordance with Louisiana Revised Statutes (RS) at the time of publication. Always check with your local wildlife authorities (Enforcement Division, Louisiana Department of Wildlife and Fisheries, USDA Wildlife Services, US Fish and Wildlife Service) for the most up-to-date rules and regulations prior to undertaking animal control activities.

From time to time, nuisance wildlife species invade crawfish ponds and in some cases cause serious damage. You can do some things but not others to take care of the problem, depending on the species.

Raccoons and otters are the most frustrating pests since they turn over traps and sometimes mash, mangle and twist the wire so badly that the trap is destroyed. Mink may swim to a few traps, consume some crawfish, and steal cut fish, but this problem is usually limited. Nutria and muskrats will dig holes in levees, costing the producer both in time repairing levees and in pumping costs to replace water (Figure 9.8). Beavers can cause problems by blocking drain pipes. These nuisance animals are classified as “fur bearers” and are protected or regulated by certain wildlife laws. During trapping season these animals may be trapped by a licensed trapper, skinned and the hides sold [RS56:259 C. (1)]. In certain other situations, farmers and landowners may trap or shoot these animals when they are a nuisance. The technicalities are different for each species, however.

Farmers and landowners can hunt raccoons and opossums with a .22 caliber rifle anytime during the year when they are found destroying crops [ RS56:116.1 C.(2)(a) ]. Raccoons also can be hunted by licensed hunters at night with at least one dog and using one .22 caliber rifle [RS56:116.1 C.(1) ]. There is no bag limit during the trapping season, but the limit is one per night after trapping season [ RS 56:116.1 C. (3) ]. The law also allows raccoons and opossums to be taken by licensed hunters during rabbit season [ RS 56:116.1 C. (4) ].

Landowners, or their designees with written permission, can use live traps for raccoons, otters, mink and muskrats and relocate the animals to suitable habitat without a permit. If live traps cannot be used, a licensed trapper can catch and dispatch these animals during trapping season. Outside of trapping season, a special Nuisance Wildlife Permit can be obtained from the district offices of the Louisiana Department of Wildlife and Fisheries (LDWF) or USDA Wildlife Services, to trap or shoot these animals when causing problems. USDA Wildlife Services offices are located in Crowley (337-783-0182), Port Allen (225389-0229) and Monroe (318-343-6499).

Nutria and beaver are considered nuisances and can be taken by trapping or shooting by a farmer or landowner without a license, except during trapping season when a trapping license is required. They can be shot only during the day (sunrise to sunset) [RS56:259 E]. Under Title 76 (Section 125) of the Louisiana Administrative code, a landowner or his designee with written permission, can trap or shoot nutria and beaver (and opossums, coyote, skunks and armadillos) during daylight hours anytime during the year when causing a nuisance. Muskrats are not included in these laws. Muskrats must be trapped during trapping season by a licensed trapper.

Poisons generally are not recommended for controlling any of these fur-bearer species. Directly poisoning nontarget species (pets and other wildlife) and secondary poisoning of animals eating on the carcasses of the dead animals are likely dangers. The only exception is the use of zinc phosphide for controlling nutria. This gray powder is a restricted-use pesticide (a private applicator's license is required to purchase this chemical) and is available from USDA Wildlife Services. Animals should be pre-baited to feeding sites for several days with carrots or sweet potatoes before applying the zinc phosphide to the bait.

The only other approved use of poison is for Norway rats and field rats. These are a nuisance around the boat and bait-cutting station, and can harbor serious and even deadly diseases. Weather resistant blocks of rat poison need to be placed in bait boxes or deep in holes or places where rats hide. The poison should not be broadcast in the open. Reducing hiding places by burning bait boxes and keeping the area clean also helps to control rats.

Birds are sometimes a problem when they feed on crawfish or turn over traps. In ponds with high numbers of crawfish, egrets and herons may not hurt the crop at all. In ponds with few crawfish, every crawfish is valuable. Egrets and herons along with ibis and seagulls are protected by federal laws and can only be harassed to leave the field. Pop guns used for blackbirds do not typically work with these birds. Pyrotechnics (fireworks) are the best thing to use to discourage these birds, but persistence is the key. Scaring the birds once a week won't do any good.

Cormorants often tip over traps in an effort to get to the crawfish or eat the fish bait. In areas where cormorants are plentiful, scare tactics are not effective without some lethal control. Federal regulations make it legal for lethal control of double-crested cormorants at “commercial freshwater aquaculture” facilities in 13 states, including Louisiana, when it is determined that cormorants are damaging an aquaculture crop. Although no special federal permit is required steps must be taken to insure compliance with federal law. First, USDA Wildlife Service personnel must confirm that damage is being done by double-crested cormorants to crawfish, and the producer must show evidence that he/she has used other established nonlethal options to minimize damage by cormorants. The USDA Wildlife Service can then issue to the producer Form 37 which allows for the lethal take of double-crested cormorants. The producer must meet the requirements of the federal depredation order, and these include the following: (1) Records (log) of the kill must be kept that include date, number killed and location. The producer must also report any accidental take of other cormorant species. Records must be kept for 3 years and a copy provided annually to the United States Fish and Wildlife Service. (2) Cormorants can be taken only within the boundary of the crawfish farming facility during daylight hours using firearms, and shotguns must use steel shot. (3) Cormorants must be disposed of by donation, burial or incineration. They cannot be traded or sold. (4) No lethal control of double-crested cormorants can be taken within 1,500 feet of nesting wood stork colonies, within 1,000 feet of wood stork roosts, within 750 feet of feeding wood storks and more than 750 feet from bald eagle nest.

A trap with only crawfish heads left in it is probably the result of turtle predation. Turtles will circle the trap and pinch off the crawfish tails that poke out through the trap wire. Turtles can be trapped using a wire “box” with an open top and sides sloping inward that allows the turtles to climb in but not out.

Fish predators can eat a significant amount of crawfish, especially in the fall when young crawfish leave their mothers. Bullhead catfish (pollywogs) and green sunfish (“bream”) are the worst culprits and are difficult to remove from the pond once they invade.

Control Methods

Developing Your Business

Attention to details during the planning and operations will increase your chances of business success in crawfish production. As with any enterprise, it is often best to start small, learning and growing into an economically viable farming enterprise. When considering a crawfish farming business for the first time, consider these factors, requirements and the following questions:

Do you have a realistic business plan developed with monthly objectives and projected cash flows for the first year and annually for each of the next three to five years?

Do you have access to capital for start-up, operation or expansion? Are your cost estimates and pricing projections reasonable? Do you have adequate cash reserves for equipment failure and other unforeseen problems?

Will a lender accommodate your production/marketing cycle?

Have you identified your primary and alternative markets?

Are the estimated profits worth your labor and resources? Is the profit potential for crawfish farming competitive with other possible investments or activities?

Are you willing to work long hard hours, daily, during the harvest season?

The economic analysis of crawfish production has evolved as the crawfish industry has grown in technology, sales and complexity. Production cost estimates and knowledge about markets are essential. Abundance of wild crawfish has a depressing effect on prices when wild and farm-raised supplies overlap. A crawfish farmer must be aware of varying market conditions and how the market changes will affect the profitability of the operation. A key to success is the understanding and estimation of production costs. Precise investment requirements, production and harvesting costs are not available for every farming situation. Projected costs and breakeven prices for various crawfish cropping systems are developed annually by the LSU AgCenter's Department of Agricultural Economics and Agribusiness and be accessed from the LSU AgCenter's Web site.

A record-keeping system is needed to generate financial reports and production records. The basic purposes of records are reporting, control, evaluation and planning, but good records can be an important resource when dealing with government crop programs or litigation. Financial reports that give the manager vital information about the business are the most important function in record-keeping. Through financial statements, a manager can determine profits (or losses), the feasibility of the business plan, the accumulation of net worth in the business and the profitability of each part of the business. Financial reports consist of income statements, balance sheets, cash-flow statements and enterprise reports.

A good records system allows the manager to see what is going on in the business, decide what is working and what is simply costing too much. A good example in crawfish farming involves multiple fields within an operation and the decision process to allocate harvesting and pumping resources. Evaluation during the year is critical to keeping costs as low as possible while increasing income. Producers often don't know how much has been spent in total or by item (bait, fuel, supplies, etc.) and therefore cannot stop wasteful practices. Financial planning for the coming year is needed to decide if sufficient net income will be generated to meet business goals. As prices paid and received change, the ability to pay bills on time and service debt can change. A projected cash flow will show the feasibility of the proposed business plan.

Production records and reports contain information about the technology used in production. It's important to maintain records of pumping time, traps used, bait (type and amount), water quality information, crawfish production time (hours, labor), results of grading and sales income per acre and per day. Careful analysis will identify the strengths and weaknesses of the production process. Future management decisions concerning forage, water, population dynamics, harvesting strategies and marketing are easier and more accurate if good records are kept. Correction of problem areas results in increased production efficiency. Also, when a crop is lost because of a natural disaster or pollution, records are needed to prove losses.

Records can be kept either in handwritten ledgers or by computer. Either method takes about the same amount of time to record information. The LSU AgCenter's Cooperative Extension Service has several publications that can be used to form a basis for your own system. These include the “Louisiana Farm Record Book” and the “Louisiana Farm Inventory Book.” Computer technology allows reports to be prepared much more easily and quickly. Computer record systems should be given careful consideration when choosing a record-keeping strategy. More experienced computer users may prefer to use spreadsheet programs rather than prepackaged business management software. Contact your local parish office of the LSU AgCenter Extension Service office for more information about financial planning for farming operations.

Records of maintenance, repairs and hours of operation should be kept for all equipment.

Whether from aquaculture or the natural fishery, the supply of live crawfish is highly seasonal, with peak of the harvest occurring from March through June (Figure 10.1). Historically, most of the domestic supply has been consumed in Louisiana and surrounding southern states, particularly Texas, the Mississippi Gulf coast and the Florida panhandle (Figure 10.2). Because of restricted geographical areas of production, seasonal supply, unstable prices and cultural mores, crawfish sales nationally have been limited, but have increased in recent years.

Product Forms

Live crawfish

All crawfish are marketed live by farmers, and live crawfish comprise most of the final sales to consumers. Producers of large crawfish have a competitive advantage, especially when the supply of live crawfish exceeds demand. In times of oversupply, generally the larger crawfish remain in the live market and smaller crawfish are processed for meat. Most producers sell live crawfish to a primary wholesaler (Figure 10.3) or a processor, although a limited volume is sold directly to retail

Figure 10.3. Marketing avenues for Louisiana crawfish.

stores, restaurants and consumers. In Louisiana, red swamp crawfish have higher consumer appeal in the live market than white river crawfish, although this distinction is usually not made outside of traditional southern Louisiana markets.

Highest demand by retail consumers and restaurants is on weekends, even in Louisiana, with limited retail sales early in the week. The live product, with its restricted shelf life of no more than several days, largely dictates harvesting schedules and market plans. Shelf life of the live product also effectively limits regional and national distribution.

Whether served in households or retail outlets, live crawfish are typically boiled (or steamed) and consumed hot and fresh in a festive atmosphere (Figure 10.4). Crawfish are not considered a staple food; rather, they are generally associated with social occasions, and no food exemplifies the Cajun cultural atmosphere like fresh, boiled crawfish coupled with its requisite condiments of spicy vegetables and cold beverages.

Processed and prepared products

When crawfish are abundant or when live markets become saturated, a portion of the annual crop is processed and sold as fresh or frozen abdominal or “tail” meat. The most popular processed product is cooked, hand peeled and deveined meat that is usually sold in 12-ounce or 1-pound packages (Figure 10.5). Tail meat may be packed with or without hepatopancreatic tissue (in Louisiana frequently referred to as “fat”), which is an important flavoring condiment in Louisiana cuisine and is savored for its distinctive rich flavor. The smaller size classes of crawfish are usually those processed for the tail meat market, leaving the larger individuals for the more profitable live market.

The abdominal meat yield for cooked crawfish is, on average, about 15 percent of live weight, but meat yield varies with factors such as sexual maturity and size. Immature crawfish generally yield 4 percent to 5 percent more meat than mature individuals because they have smaller claws and thinner shells. Cooking time and peeling technique can also influence meat yield because all processing is by hand. Early in the production season (November-March) when a high percentage of the crawfish are immature, meat yield can be as high as 22 percent to 23 percent. Late in the season (April-July) when most crawfish are mature and have heavier exoskeletons and large claws, meat yield can be as low as 10 percent to 12 percent of body weight. Abdominal meat is used in diverse ways and can be an appropriate substitute in many shrimp recipes. The amount of crawfish processed for tail meat in Louisiana varies annually, but since the introduction of inexpensive procambarid crawfish meat from China, it is estimated that less than 10 percent of the annual crop is now processed for meat.

Another product form is cooked whole crawfish, usually served fresh and hot, with small volumes also sold as frozen product later to be warmed and served. Traditionally, crawfish in the southern United States are cooked with red pepper-based spices/seasonings, often with onions, potatoes and corn that complement the meal. The consumer extracts the edible portions of the whole crawfish by hand (Figure 10.6).

Increasing in popularity in Louisiana, and within the range of delivery for live crawfish outside of Louisiana, are retail outlets and restaurants serving hot, boiled crawfish. Small, seasonally “take-out” outlets (Figure 10.7) have developed wherever live crawfish can be readily obtained, and many businesses also cater boiled crawfish to large groups, parties and festivals using custom boiling rigs (Figure 10.8).

Prepared frozen crawfish dishes, although still only encompassing a small portion of total sales, have helped increase the distribution of processed abdominal crawfish meat through value-added products.

Marketing Influences

Marketing of domestically produced crawfish has been complicated in recent years by imports of crawfish products. Millions of pounds of imported frozen processed meat and whole boiled procambarid crawfish, principally from the Peoples Republic of China, are imported into the United States annually (Figure 10.9). Although a tariff has been imposed by the United States Department of Commerce on much of the imported Chinese crawfish meat, damage to the U.S. industry has occurred. Prior to Chinese imports over 100 licensed crawfish processors existed in Louisiana. Today, the number of processors number in the low 30s and this has lead to dramatic reduction in processing (peeling) capacity in Louisiana. As a consequence, each year thousands of tons of smaller crawfish are not harvested for lack of adequate live markets and processing infrastructure.

Although demand for crawfish in Louisiana is high, and markets are expanding in adjacent states, on a national basis, crawfish are in direct competition with products such as shrimp, prawns, lobster and crabs. Unlike Louisiana, the public in other states have historically and culturally not consumed crawfish. Nonetheless, crawfish imports provide for year-round availability and more stable prices, which reportedly have had some positive influences in development and expansion of new markets for crawfish products outside of traditional crawfish consuming areas. The growing popularity of southern Louisiana “Cajun” and “Creole” cuisine throughout the United States offers excellent opportunity for expanded market development and sale of both live and processed domestically produced crawfish products in the southern United States and elsewhere.

Pricing

Supply and demand relationships are reflected in price variations from year to year and from week to week during the crawfish harvest season. In Louisiana, average annual pond bank price paid to producers from 1997 through 2005 has averaged between $0.55 and $0.82 per pound, when annual supply ranged from 70 to 85 million pounds, except in 2000 and 2001 when low supply from both aquaculture and the wild crop pushed average statewide wholesale prices over $1.24 per pound (Table 10.1). Seasonally, prices to producers are highest in winter and early spring when supply is relatively low (Figure

10.1 and Table 10.2). Prices decline significantly in late spring and summer when supply peaks and the supply and demand for other locally produced fresh seafoods such as shrimp and crabs increase. In Louisiana, price declines as high as 40 percent to 55 percent for “field run” crawfish can occur within several weeks during peak production (April and May) if crawfish quality (usually size) decreases, but the drop in price for larger crawfish is usually substantially less. In recent years, large crawfish have commanded a wholesale price 2 to 3 times higher than paid for medium to small crawfish.

Although prices for live crawfish are relatively uniform among wholesale buyers from day to day or week to week, no single buyer or group of buyers exerts excessive control over pond-bank prices. But when crawfish supplies are high, wholesalers and processors do have the ability to exert price leverage on producers, and this is usually based on their ability, or inability, to move large volumes of crawfish in the live market. Some buyers offer premium prices for their larger, more loyal or more consistent suppliers.

Although wholesale prices for peeled crawfish tail meat are not published, prices typically track the price of live product and, as a “rule of thumb,” the wholesale price of a pound of tail meat is 10 to 12 times higher than the wholesale price of a pound of live crawfish.

Production Strategies for Identified Markets

A crawfish producer should be familiar with potential markets, both wholesale and retail, and match production to estimated needs. Since crawfish are harvested several times per week, reliable buyers are paramount to a farmer's success. Direct sales to retail customers by farmers are not particularly high in large production areas like southern Louisiana. Therefore, most large producers in these areas must sell most of their harvest to wholesale buyers and processors. Small-scale crawfish producers outside of Louisiana have few established and knowledgeable wholesalers who are experienced in marketing live crawfish. Many small-scale producers, however, have successfully developed markets for both direct retail sales to consumers and to retail seafood establishments.

Occasionally, harvesting schedules and strategies must be adjusted to accommodate available markets. Buyers may prefer to have product delivered only on certain days, such as Thursday through Sunday. Additionally, market demand for crawfish early in the season may allow for various sizes of crawfish to be sold with little problem, but when crawfish supplies are more abundant, trapping strategies may need to be adjusted to maximize crawfish sizes, even at the expense of overall yield. Planning and good communication with potential buyers early in the season can allow trapping strategies to be developed that respond to market preferences and improve a producer's competitive position.

Regulations and Permits

Various permits may be required to market crawfish, such as wholesale or retail fish distributor's license, or to transport them across state lines. Permits are specific for each state. Imports of live non-native crawfish are restricted or forbidden in a number of states, especially where there are concerns over establishment and competition with native species. Before shipping live crawfish, always verify regulatory requirements in the receiving state, or states in which crawfish are being transported, to avoid serious legal problems.

In Louisiana, live haulers are usually required to possess permits or licenses to transport crawfish, depending on whom their crawfish are being purchased from or sold to. These may include municipal or parish permits as well as a state transport license and seafood wholesale/retail dealer's license. For interstate shipments of live crawfish, pass-through states and the receiving state also will likely have license requirements.

Transport and Storage

Storage and transport of live crawfish is unusual in that they are not transported in water, but rather consolidated in plastic mesh sacks (Figure 10.10). Sacks hold about 35 to 45 pounds of crawfish depending on how tightly the trapper chooses to pack them. This method is preferred over more rigid containers such as totes (Figure 10.11) because crawfish can be packed in the sacks in a manner that prevents damage from pinching, which can happen when animals are not sufficiently restricted.

To minimize crushing, sacks should not be packed too tightly, but sufficiently tight to restrict crawfish movement. Sacks of live crawfish can be transported in open bed trucks for short distances, but sacks should be covered with a tarp to minimize drying of gills. Wholesalers or jobbers haul sacks of live crawfish over long distances, or in larger quantities, in insulated trucks, with or without refrigeration (Figure 10.12). Crushed ice is placed over the sacks in nonrefrigerated trucks and, in some cases, refrigerated trucks, to reduce crawfish metabolism and maintain a high level of humidity, which increases shelf life of live crawfish.

High survival rate during live transport begins by insuring crawfish are harvested from ponds with good water quality. Live crawfish should be transported to on-the-farm coolers or to the terminal market as soon after harvest as possible. Transport vehicles should be clean and free from petroleum products or other contaminates. If hauled long distance in the harvest boat or transported in an open vehicle, exposure of crawfish to excessive wind and bright sunlight should be minimized by covering the sacks with wet burlap or a tarp. Sacks should not be stacked so high that crawfish in the bottom sacks are crushed.

Sacks of live crawfish in good physical condition can be held in high humidity coolers at 38 F to 46 F for up to several days prior to peeling or further transport to the terminal destination. Maintenance of gill moisture is crucial for survival of crawfish held in coolers. Gill moisture is usually accomplished by periodic wetting of crawfish and/or placement of wet burlap or ice over the sacks of crawfish. If placed in plastic tote boxes, the top tote should be filled with ice. Melting ice trickles down through the totes to provide the necessary moisture. Placing unchilled crawfish in totes is not recommended because physical damage from pinching by active crawfish may occur.

A relatively small volume of live crawfish is shipped in sacks by air-freight throughout the United States in insulated seafood shipping boxes containing frozen gel packs. During warm weather, crawfish shipped by air freight should be cooled overnight prior to shipping.

Purging and Cleaning

To provide a more appealing product for live markets, a small number of producers have adopted the practice of “purging” crawfish before selling them. This requires that crawfish be confined in water or very humid environments where food is withheld for 24 to 48 hours. This process cleans the exoskeleton of mud and debris and eliminates or reduces digesta in the

Figure 10.12. Crawfish transport truck and transport with ice.

intestine (Figure 10.13), which consumers may find unappealing. This method should not be confused with the practice of immersing crawfish in salt water immediately before boiling, which is not effective in evacuating the gut and is little more than an external wash.

To facilitate removal of the intestinal contents, crawfish are commonly held in tanks within specially constructed boxes or baskets (Figure 10.13) that are usually suspended in water. Recommended loading rate is about 1.5 pounds of crawfish per square feet of submerged surface area with adequate aeration and water exchange. Equally effective, but seldom used, is a water spray system where crawfish are held in shallow pools of water (1/2-inch deep) under a constant spray or mist. Holding crawfish in aerated vats or purging systems under crowded conditions for more than 24-48 hours is not recommended because of the possibility of excessive mortality. Though purging increases the cost of the product, purged crawfish have high consumer acceptance, particularly outside of traditional Louisiana markets. Some people who have eaten crawfish for many years are accustomed to nonpurged crawfish and do not find them objectionable; nonetheless, many would probably prefer purged product if cost was reasonable.

Although the current market for purged crawfish is small from a lack of public awareness and price differences (15 percent to 25 percent higher), purging has contributed to repeat sales and loyalty to certain producers or distributors. Mortality during purging is the largest contributor to increased prices, but research has recently demonstrated that shorter purge duration (12 hours) can be nearly as effective and contributes significantly to less mortality.

The external surfaces of crawfish, which can be fouled and/or stained, are reasonably cleaned during purging. Abrasive actions of crowded crawfish rubbing against one another effectively “polish” the shells. For nonpurged animals and excessively stained batches of crawfish, however, additional cleaning is sometimes accomplished prior to cooking. External cleaning of the carapace of live crawfish with food-service chemicals (ascorbic or citric acid and baking soda) to enhance appearance and increase marketability is becoming increasingly common.

Grading

Crawfish markets have changed considerably since the mid-1980s when crawfish were sold without consideration of size. Development of an export market in Scandinavia in the late 1980s for crawfish 15-count (number per pound) or larger, first provided the impetus for size grading. Louisiana's export markets for crawfish were eventually lost to competition from the Peoples Republic of China, but size grading remained and is widely used in the domestic market. Grading by size is usu-ally not practiced early in the production season when crawfish supply is low and demand is high for crawfish of all sizes, but as the volume of crawfish increases in early spring size grading becomes a standard practice for servicing the market demand for large crawfish. Nearly all grading occurs at wholesale outlets or processing plants, using modified vegetable graders or custom-made graders (Figure 10.14).

At present, no uniform size and grade standards exist for the crawfish industry as with other seafoods, and this to some degree hinders out-of-state market development and expansion. Based on a number of production and marketing conditions, crawfish are typically graded into two or three size classes. Generally, the largest crawfish are sold to specialty restaurants, and the smaller ones are processed for tail meat or blended with larger individuals for large volume sales. One example of a commonly used grading system for crawfish in Louisiana is shown in Table 10.3. Other grading standards are used by various crawfish wholesalers depending on their markets.

Table 10.3. Example of a common grading system used for live crawfish in Louisiana.

Size Classification Size Classification Number (Count) of by Number Crawfish per Pound

Large 1 15 or fewer Medium 2

16-20 Small 3 21 or more Field run Mixed sizes

Abdomen – Refers to the tail of a crawfish. Used in locomotion and swimming. Peeled after cooking for consumption.

Age class – Also synonymous with size class, recruitment class. Generally refers to pulses or “waves” of crawfish hatched around the same time. For example, if large numbers of crawfish were hatched and released into the water in the first two weeks of October and the last two weeks of November, two age classes of juvenile crawfish would be in the pond. (Also see “Recruitment.”)

Agronomic – Refers to terrestrial plant agriculture.

Aquaculture – Cultivation of aquatic organisms in a controlled and managed environment.

Baffle levees – Small levees built within the interior of a crawfish pond to direct water flow when pumping water into ponds.They also serve as reproductive burrowing area for crawfish.

Biomass – The weight of all the organisms forming a given population or inhabiting an environment. Can also be used to describe the total quantity or weight of plants, as in biomass of the forage crop.

BMP – “Best Management Practices”; procedures followed by agricultural producers to control the generation and delivery of pollutants from agricultural activities into water resources of the state thereby reducing the amount of agricultural pollutants entering surface and ground waters.

Authors

W. Ray McClain, Ph.D., Professor, Rice Research Station

Robert P. Romaire, Ph.D., Professor and Resident Director, Aquaculture Research Station

C. Greg Lutz, Ph.D., Professor, Aquaculture Research Station

Mark G. Shirley, Area Fisheries and Aquaculture Agent, Louisiana Cooperative Extension Service

Contributors

Jimmy L. Avery, Ph.D., (formerly Associate Specialist in Aquaculture)

Wendell Lorio, Ph.D. (formerly Associate Specialist in Aquaculture)

Acknowledgments

This publication was partially funded by the Louisiana Crawfish Promotion and Research Board, as was much of the research reflected in these recommendations.

The authors would like to acknowledge the contributions of Mr. Laurence W. de la Bretonne Jr., Dr. James W. Avault Jr. and Dr. Jay V. Huner to the development of Louisiana's crawfish farming industry.

Mr. de la Bretonne served as state aquaculture extension specialist with the LSU AgCenter's Louisiana Cooperative Extension Service for more than15 years prior to his untimely death in 1991.

Dr. James W. Avault Jr. was a crawfish researcher and teacher with the LSU AgCenter's Agricultural Experiment Station for 30 years. He retired in 1996.

Dr. Jay V. Huner was a crawfish researcher and teacher at Southern University in Baton Rouge for 13 years and later became the director of the Crawfish Research Center, University of Louisiana at Lafayette, for 17 years. Dr. Huner retired in 2005.

Mr. de la Bretonne and Drs. Avault and Huner were all recognized as international authorities on the culture of Louisiana crawfish and all influenced to a large degree the development of crawfish farming in Louisiana as we know it today.