Native Aquatic Species of the Gila River Basin
in Arizona and New Mexico
Crayfish (Orconetes virilis and Procambarus clarkii)
Seventy five percent of the world's crayfishes (390 native species) can be found in North America. However, no native crayfish occur in Arizona or the Colorado River basin of western North America.
Crayfish are decapod crustaceans that inhabit every continent except Africa and Antarctica (Fernandez and Rosen 1996). In their natural habitat they are important detritivores (eating loose organic material) serving to increase available nutrients, and they may at times provide up to two-thirds of the diet of members of the sunfish family (Roell and Orth 1993 as cited in Fernandez and Rosen 1996). Pennak (1989) describes crayfish as omnivores that eat aquatic vegetation as well as snails, small fish, and aquatic insects.
However, in several well documented cases, non-indigenous crayfishes have greatly altered North American lake and stream ecosystems, harmed fisheries, and extirpated populations of native crayfishes (Hyatt 2004). They also have a strong potential to impact native fish reproduction via predation on juveniles and eggs (Mueller et al 2006).
Crayfishes first appeared in Arizona about 30 years ago when they were stocked by the Arizona Game and Fish Department and US Fish and Wildlife Service for the purposes of aquatic weed control and as forage for sport fishes (Hyatt 2004). The negative impacts that non-indigenous crayfish can have on stream ecosystems in Arizona has been well documented by a study conducted in the White Mountains by Fernandez and Rosen (1996). Where crayfish were abundant, native leopard frogs were rare or not present, aquatic snails were eliminated, diversity and abundance of aquatic insects was reduced and aquatic vegetation was severely reduced.
Fernandez and Rosen (1996) also described an inverse relationship between the abundance of garter snakes and crayfish in Eagle Creek and the Blue River. Crayfish have even been implicated in the decline of Sonoran mud turtles, likely through predation on hatchlings. They concluded that introduced crayfish presented a significant danger to the ecological stability of Arizona's stream habitats (Fernandez and Rosen 1996).Work Cited:
Hyatt, M.W. 2004. Investigation of crayfish control technology. Final report (No.1448-20181-02-J850) to Arizona Game and Fish Department.
Pennak, R.W. 1989. Freshwater invertebrates of the United States, Protozoa to Mollusca, 3rd Edition. John Wiley and Sons, New York.
Roell, MN.J., and D.J. Orth. 1993. Trophic basis of production of stream-dwelling smallmouth bass, rock bass, and flathead catfish in relation to invertebrate bait harvest. Transactions of the American Fishery Society 122:46-62.
June 25, 2009
Joseph J. Billerbeck - email@example.com