Traditional culture:
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. 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.
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.
Authors:
Louis R. D’Abramo, Cortney L. Ohs, Terrill R. Hanson and Jose L. Montanez
