Annual yields in small experimental ponds have consistently been 1,800 to 2,300 pounds per acre (2,017 to 2,578 kg/hectare), although some lower and higher yields have been recorded.
Recent results from large commercial ponds verify that these yields can be expected. The monthly proportional distribution of annual yield is presented in Table 3. Individual harvest weight is highest from September through April, ranging from about 1.0 ounce (28 g), 16-count, to 0.8 ounce (22.4 g), 20-count.
When the number of crawfish in the pond is highest (usually May through mid- August), the harvest weight decreases slightly to about 0.67 ounce (18.8 g), 24-count. Using 3 /4-inch square mesh traps will probably result in lower mean weight and higher yield.
Processing:
Crawfish harvested from semiintensive systems are processed in the same manner as those harvested from forage-based ponds. The crop can be marketed as whole (live or frozen) or as peeled tail meat, depending upon demand and ultimate destination.
Live crawfish are generally packed into open mesh vegetable sacks and kept moist under refrigerated storage (usually for no more than 3 days) until eventual transport and distribution.
Sometimes live crawfish are held in tanks filled with water for 12 to 24 hours to allow “purging” of any partially digested food from the intestinal tract before they are placed in refrigerated storage or frozen.
Purging makes the product more attractive to the consumer by removing mud from the gill chambers and the shell. Some crawfish may be lost during the purging procedure, but this is offset by the higher price of a value added product. Live crawfish can be processed in individually quick frozen (IQF) systems.
For this method of processing animals must be live because post-mortem release of proteolytic enzymes from the digestive gland can cause the tail muscle to lose its natural firmness. Shelf life of IQF product is 4 to 6 months.
The longer harvest period possible with semi-intensive culture raised concern about changes in tail meat quality over time. Sensory evaluation panels at Mississippi State University tested crawfish harvested at different times of the year for an array of sensory properties. Crawfish were boiled without seasoning for sensory evaluation on the same day they were harvested.
Analytical tests of shell rigidity and muscle shear were conducted on the same group of crawfish. No significant changes in quality, based upon the time of year of harvest, were detected, except for an increase in shell hardness during mid- to late July and early August. This seasonal change is not likely to affect consumer appeal.
Crawfish are divided into three size grades:
- peeler — > 21 count, 0.75 of an ounce (21 g);
- restaurant — 21 to 15.5 count, 1.04 ounces (29 g); and
- export — < 15.5 count.
Grades correspond to the preferred destination of each of the categories. The export term is irrelevant, however, because virtually no crawfish are exported. Export grades generally predominate during cooler months (October, November, March and April), while the restaurant and peeler grades predominate from April to September.
Some seasonal size difference is related to more frequent harvests during warmer months when growth rates are higher. Harvesting more often increases yield while reducing harvest size.
Other management needs:
Invasion of ponds by fish
Invasive fish species must be kept out of ponds to achieve maximum annual production in semi-intensive systems. Fish compete with crawfish for feed and natural food organisms. Green sunfish and bullheads of sufficient size consume young crawfish.
The magnitude of the problem is directly related to the number of fish in the pond. If large numbers of small fish are caught in crawfish traps, or if fish are observed along the perimeter of the pond or feeding in the water column, there is apt to be a serious problem.
Ponds must be drained to remove large numbers of fish. When surface water is used to fill the pond, an appropriate size screen must be in place to prevent the introduction of fish and fish eggs. Fish also may enter through the pond drain during overflows.
Smaller ponds, 5 acres or less, are less likely to become a depository for fish or fish eggs introduced by birds and are easier to manage if a fish invasion does occur. The best time to remove fish from production ponds is mid-August to mid-September when harvest is often suspended because of low CPUE.
The pond should be drained approximately 1 foot, left for a week, then drained another 1 foot, etc., until it is completely drained. This gives crawfish time to burrow temporarily into the pond levee or bottom. Once the water is shallow enough, fish can be seined. When the pond is completely drained, any remaining fish are removed.
Fish populations also can be eliminated by applying rotenone when the water is fairly shallow. Rotenone is a restricted-use pesticide and its application requires specific permitting. After fish are removed, the pond should be refilled.
Authors:
Louis R. D’Abramo, Cortney L. Ohs, Terrill R. Hanson and Jose L. Montanez
