CRAYFISH

Crayfish, sometimes called crawfish, crawdads, mudbugs, yabbies, or spoondogs, are freshwater crustaceans resembling small lobsters, to which they are closely related.

Identification, Range and Biology
Crayfish, also called crawfish, crawcrab, crab, stonecrab, crawdad, creekcrab, and other local names, are native to fresh waters on all continents except Africa, where they have been widely introduced. There are over 400 species in the family Astacidae worldwide, and approximately 300 species in the United States. In size, shape, and color, the variation is extremely wide among species. The detailed life histories and habits of all species of crayfish are beyond the scope of this handbook.

Crayfish are economically important in a number of states for use as fish bait and for human consumption. In Louisiana, the crayfish is a major economic crop and comprises the second largest aquaculture industry in North America. Over 130,000 acres (56,000 ha) are devoted solely to crayfish culture.

Damage
Most damage associated with crayfish is the result of crayfish burrowing in home lawns. Burrows created by burrowing species of crayfish are damaging to turf areas and may be hazardous to mowing machinery. Newly planted rice fields may be damaged by foraging crayfish where local populations are high.

Crayfish populations in commercial baitfish ponds can reduce reproduction by feeding on the eggs of the baitfish as they are deposited on spawning mats. During pond harvest, crayfish caught in the nets injure and destroy baitfish as they are being harvested for market.

Unwanted populations of crayfish have been established in the wild because of the release of bait crayfish. Some populations have reached extremely high levels. Crayfish can reduce game fish populations by preying on eggs and fry. They also can degrade habitat by destroying aquatic vegetation.

Legal Status
Crayfish may be protected by law in some states. Harvest of crayfish may also be regulated by state wildlife conservation agencies. In areas where damage occurs, control measures are generally unrestricted. Check with your local agricultural or wildlife authorities before initiating control. Unwanted populations of crayfish have resulted in regulations against the use of crayfish as bait in some northern lakes.


Damage Prevention and Control Methods

Exclusion
Not practical.

Habitat Modification
Deep tillage destroys burrows and generally results in lower populations. Drainage of rice irrigation systems and fields during fall and winter months reduces populations.

Repellents
None are registered.

Toxicants
None are registered. Check individual state regulations for Special Local Needs registrations 24(c). Approved turf insecticides used for insect pest control will also control crayfish in lawn and turf areas.

Fumigants
None are registered. Check state regulations for Special Local Needs registrations 24(c).

Trapping
Not effective in eliminating populations. May be used in capturing crayfish for bait or food.




ACKNOWLEDGEMENTS
The above information was adapted from PREVENTION AND CONTROL OF WILDLIFE DAMAGE with permission of the editors, Scott E. Hygnstrom, Robert M. Timm, and Gary E. Larson (Cooperative Extension Division, Institute of Agriculture and Natural Resources University of Nebraska-Lincoln, United States Department of Agriculture Animal and Plant Health Inspection Service, Animal Damage Control, Great Plains Agricultural Council Wildlife Committee).