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 rapidly—before it is consumed—so it mainly acts as a fertilizer and a source of nutrition 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.
Water quality:
Red swamp crawfish can tolerate poorer water quality conditions than many species of fish and crustaceans. They can tolerate levels of dissolved oxygen as low as 0.5 mg/L, but chronically low levels are not conducive to maximum growth.
If levels fall, or are anticipated to fall, below 3 mg/L, ponds should be aerated using PTO-driven paddlewheels or floating electrical aerators at a rate of 1.5 hp/acre (0.6 ha).
Most problems with low concentrations of dissolved oxygen occur from May through August when water temperatures are highest and crawfish populations are largest.
The more crawfish there are, the higher the oxygen demand. The concentration of dissolved oxygen near the pond bottom should be monitored daily using an oxygen meter or some type of analytical test kit.
The best time to monitor is just before sunrise when levels are generally lowest. If the oxygen level is chronically low, monitor more often to be certain it does not fall to a lethal level.
At times the pond may become stratified, causing the bottom layer to be depleted of oxygen. This can be prevented by mixing the water in the pond.
If the pH of the soil of the pond bottom is less than 7.0, lime should be added until the pH is at least 7.0. The ideal pH of water used to raise crawfish is 7.0 to 9.0. The total hardness and total alkalinity of the water should range from 50 to 250 ppm as calcium carbonate.
If primary productivity is high and water has a high alkalinity and low total hardness, the pH will tend to be too high. High pH can be managed by applying either agricultural gypsum (Ca SO4) or alum (AlSO4). Alum applied at a rate of 1 mg/L of water gives almost immediate results to prevent mortality, but the effect is only temporary if primary productivity remains high.
Agricultural gypsum is a good source of calcium that will reduce high levels of carbonate through its precipitation as calcium carbonate. Applying gypsum to achieve a total harness equivalent to total alkalinity will lower pH to an acceptable level.
Authors:
Louis R. D’Abramo, Cortney L. Ohs, Terrill R. Hanson and Jose L. Montanez
