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New Crops News, Spring 1994, vol. 4 no. 1

Crayfish: New Aquatic Crop for the Midwest

In the United States, approximately 80% of the fish and shellfish consumed are harvested from wild populations. The world's oceans have been bountiful, but we are at the end of this supply. According to most fishery managers, the oceans are at maximum sustainable yield. We will not be able to harvest more pounds of fish and shellfish. At the same time, world population and per capita consumption continue to increase.

The demand for fish products is increasing because of consumer acceptance and perceived health benefits. The medical community continues to report that fish are healthy food items. Fish and shellfish are also one of the leading contributors to our national trade deficit, often ranking second only to petroleum products. These problems can be reduced by raising our own fish and shellfish. This represents a potential contribution to farm diversification in Indiana and throughout the country. We at Purdue, as well as other land-grant universities in the Midwest, have been exploring the possibility of raising fish and shellfish in our climate. Several species have been the focus of our initial research efforts. Those species are classified as cool water animals; that is, they grow best when reared at cool water temperatures, which we have in this region.

Initial research efforts at Purdue have been with hybrid striped bass, yellow perch, hybrid bluegill, and native species of crayfish. All of these initial efforts can be characterized as successful. It takes either one or two growing seasons to produce a marketable-size animal, depending on species chosen. It takes two growing seasons to produce a marketable-size catfish in Mississippi.

Crayfish

Crayfish production in Louisiana is the second largest aquacultural industry in the United States. Louisianans eat about 90% of their production, and thus, there is little export to the Midwest. However, crayfish culture in the South is a seasonal activity. Crayfish are typically produced from December through June, which coincides with the activity patterns of the species native to that area. The activity pattern of crayfish native to Indiana is exactly offset.

Native species of crayfish produce young in April-May, and those juveniles grow through the spring and summer. Marketable-size crayfish have been produced in one growing season (harvested in October or November). Feed for pond reared crayfish include agriculture forages such as wheat straw and alfalfa, so the cost of production is relatively low. There is an opportunity to fill a market niche in one of the largest aquacultural industries in the United States with a native species.

Crayfish markets are divided into two distinct outlets, hard- and softshell. Hardshell crayfish are the form typically considered as food for human consumption. The tail muscle is the edible portion, similar to shrimp or lobsters. Production of hardshell crayfish has been increasing, and the prices obtained in the marketplace have been excellent. Crayfish in Louisiana sell for $0.15-1.00/lb., whereas crayfish in Indiana have been selling for $3.00/lb. live weight without delivery. A series of crayfish "boils" have been successful in the Lafayette area, and each time, more people are willing to consume crayfish.

The other important market form for crayfish is softshell. Crayfish must molt in order to grow. Immediately after a molt, the entire animal is soft and edible. As many of you know, softshell crayfish as a fish bait is very popular and effective. It is also one of the largest aquacultural industries in Indiana. Recent research at Purdue has developed optimal conditions for producing softshell crayfish for the human food market, similar to softshell blue crabs on the East and Gulf Coasts.

Optimal temperature for molting adult crayfish is approximately 66°F, while optimal temperature for molting juveniles (for the bait market) is approximately 77°F.

The only means of producing softshell crayfish is in tanks in a controlled situation. This requires a nutritionally complete food. In a series of studies conducted at Purdue, several key nutritional requirements for crayfish have been identified. These include a need for vitamin C in the diet as well as preferred forms of vitamin A. Vitamin C is required by humans, guinea pigs, fish, and now crustaceans; all other animals can synthesize vitamin C from other compounds. If an inappropriate form of vitamin A is fed to crayfish, they develop a blue pigmentation and exhibit reduced weight gain. Crayfish also require a different source of dietary carbohydrate in their diets, glucosamine instead of glucose. By-product feeds such as shrimp-head meal contain abundant levels of these compounds and are inexpensive in the marketplace.

Prospects

The opportunities for aquaculture in the Midwest are excellent. Much of the technology necessary to successfully grow aquatic animals can be linked in a combined hydroponics/aquaculture system.

For further information, contact LaDon Swann, Purdue's Aquaculture Extension Specialist (765/494-6264), or Paul B. Brown, Associate Professor of Aquaculture (765/494-4968). Another good source of information is the Indiana Aquaculture Association. For more information on the Association and Directory of current producers contact:
Ernie Bailey, Secretary/Treasurer
1821 E County Rd 400 South
Greensburg IN 47240
(812/663-7109)

Paul B. Brown