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Semi-Intensive Production of Red Swamp Crawfish

by 5m Editor
9 January 2006, at 12:00am

Louis R. DAbramo, Cortney L. Ohs, Terrill R. Hanson and Jose L. Montanez and published by the Southern Regional Agricultural Center and the Texas Aquaculture Extension Service - Traditional pond culture of crawfish (Procambarus clarkii and P. zonangulus) is extensive, with little energy input and no feed directlyprovided. Crawfish are produced in an annual cycle with an agronomic crop, commonly rice. Rice fields are planted and then graduallyflooded to a depth of 0.3 to 0.7 m.

Semi-Intensive Production of Red Swamp Crawfish in Earthen Ponds without Planted Forage - Louis R. DAbramo, Cortney L. Ohs, Terrill R. Hanson and Jose L. Montanez and published by the Southern Regional Agricultural Center and the Texas Aquaculture Extension Service - Traditional pond culture of crawfish (Procambarus clarkii and P. zonangulus) is extensive, with little energy input and no feed directly provided. Crawfish are produced in an annual cycle with an agronomic crop, commonly rice. Rice fields are planted and then gradually flooded to a depth of 0.3 to 0.7 m. Southern Regional Agricultural Center

Traditional culture

After flooding, crawfish emerge from their burrows. The farmer may choose to harvest both rice and crawfish or only crawfish. If the rice is harvested, regrowth, called ratoon, occurs. After harvest and as air temperatures decrease to freezing, the ratoon or the unharvested rice dies and begins to decompose. Bacteria and algae that grow on decomposing plant material are consumed by organisms that, in turn, are food for the crawfish.

Crawfish can be harvested with traps as early as November, but are usually harvested from January through May. Harvest may end before May in response to a successful harvest from the capture fisheries or the need to plant a new crop. For a more detailed description of these production practices, refer to SRAC publications 240, 241 and 242.

Limitations of traditional culture

Culturing crawfish with planted forage has helped to satisfy the increasing consumer demand for crawfish and to prolong the season when crawfish are available. However, when the harvest from the capture fisheries is abundant, prices often fall below the level at which the culture fisheries can realize a profit. Traditional crawfish farming has other limitations. The decay of vegetation in shallow water can produce critically low dissolved oxygen concentrations, particularly when water temperature is high. Also, food resources are sometimes depleted by mid-March or early April, when the population of crawfish is largest. As a result, crawfish cease to grow, or become stunted, and many of them remain below market size.

Trapping is the only harvesting method that can be used in shallow water that contains vegetation. Seining is not possible when vegetation is present. Planted forage also limits the growth and harvest period. The pond must be drained and the crop allowed to grow before the pond can be reflooded. If flooding occurs when water is warm, accelerated rates of decay will cause the dissolved oxygen in the water to decrease to levels that are stressful or even lethal. If flooding happens when water is cool, water quality is not as likely to be a problem but the cooler water is not conducive to rapid growth of the red swamp crawfish.

An alternative culture

Growing crawfish in deeper ponds without planted forage has several advantages over traditional crawfish culture. The growing and harvest seasons are longer; there are fewer problems with low levels of dissolved oxygen; and deeper ponds without forage can be seined to rapidly remove excess crawfish and prevent stunted growth.

Management practices

Pond design and water supply
Ponds should have an average depth of about 4 feet, range in size from 1 to 5 surface acres of water, and have a 3:1 slope from the top of the levee to the pond bottom. Long, narrow, rectangular ponds are more suitable than wide, square ponds because they make it easier to distribute feed or organic fertilizer over the entire surface area of the pond. There is also more space for crawfish to burrow along the perimeter of long, rectangular ponds. Narrow ponds also have a larger area of shallow water that presumably serves as a nursery or sanctuary for juveniles.

Either surface or ground water can be used to fill ponds. The lower cost of using surface water must be weighed against having a reliable quality and quantity of water. Surface water can contain predatory fish that compete with crawfish for the natural food in the pond. Once ponds are filled, additional water is needed only to replace what is lost from evaporation. Ponds are generally not drained unless they become contaminated with fish.

Initial stocking

After the pond is prepared and filled, it is stocked with broodstock obtained from commercial capture or culture fisheries. Stocking can be done from May to July. Broodstock generally consists of an equal number of males and females. Stocking density should be 75 to 100 pounds per acre (84 to 112 kg/hectare). Be sure to stock only crawfish harvested within the previous 24 hours.

Crawfish held for longer periods of time are subject to stress and may have significant post-stocking mortality. Broodstock should be transported in mesh sacks and packed densely enough to minimize movement. The transported crawfish should be kept cool and moist, but not have direct contact with ice. If sound management practices that ensure good survival are followed, crawfish should not have to be restocked annually. The unharvested population remaining in the pond should be sufficient to sustain consistent levels of production from year to year. Restocking is recommended when annual production in a pond is significantly lower than in all other ponds or when it decreases by 25 to 30 percent over time. Broodstock should be restocked at a rate proportional to the decrease in production.

Feeds and feeding strategies

Existing ponds do not need to have a food source added before stocking because natural foods should be sufficient to sustain the population until the first young of the year (those hatched during successive spawnings of a calendar year) are produced in mid-fall.

However, new ponds should be organically fertilized (with cracked corn, cotton seed meal, or distillers dried grains) before and after stocking to ensure sufficient natural food. Once the initial young of the year have hatched, a formulated feed (a combination of organic fertilizer and feed, or just a fertilizer) must be added to the pond to enhance the production of pond organisms. Both a pelleted, 32% crude protein, sinking catfish feed and a comparably priced extruded, 28 to 30% crude protein, sinking diet have been successfully used in experimental trials. The food breaks up rapidlybefore it is consumedso it mainly acts as a fertilizer and a source of nutri- tion for microorganisms that, in turn, are food for those organisms crawfish eat. For direct consumption by crawfish, it is best to use a highly water-stable, extruded, formulated feed.

If the price of feed becomes costprohibitive, alternative methods of fertilization will be necessary. For example, two-thirds of the amount of a sinking catfish feed might be replaced with alfalfa or range pellets. Or, commercial feed could be supplemented with or replaced by an organic fertilizer such as corn, alfalfa hay, cottonseed meal, or soybeans. In recent research, a combination of rejected soybeans and alfalfa hay (composite level of crude protein = 28%) was substituted for formulated feed with no significant differences in production.

The recommended feeding (fertilization) rates for each month are presented in Table 1. These amounts translate into daily feeding (fertilization) rates of 5.6 to 31.5 pounds per acre (6.3 to 35.3 kg/hectare). These are estimates based upon the biomass (total weight) of the pond population and the water temperature. Crawfish eat less as water temperature decreases and eventually stop eating at temperatures less than 50 F (less than 10 C), within its range of tolerance. Crawfish feed and forage most actively during the evening. However, because feeding is essentially a pond fertilization process, it should be done in mid-afternoon when the level of dissolved oxygen is comparatively high. Whether feeding (fertilization) needs to be done every day has yet to be established.

There are many fertilizers, in a range of prices, that could be used. Pelleted feed is easier to distribute than feedstuffs. Pelleted organic fertilizers include corn gluten, rice bran, alfalfa pellets and range pellets. Organic fertilizer should be used with care, however, particularly if the temperature of the water is high, because it can dramatically reduce dissolved oxygen.

Further Information

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Source: Southern Regional Agricultural Center and the Texas Aquaculture Extension Service - Taken from site - January 2006

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