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Interactions between an Exotic Crayfish and Stocked Rainbow Trout in Newcastle Reservoir, Utah
Author(s) -
Hepworth Dale K.,
Duffield Daniel J.
Publication year - 1987
Publication title -
north american journal of fisheries management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.587
H-Index - 72
eISSN - 1548-8675
pISSN - 0275-5947
DOI - 10.1577/1548-8659(1987)7<554:ibaeca>2.0.co;2
Subject(s) - crayfish , rainbow trout , fishery , biology , predation , stocking , salmo , trout , carapace , ecology , zoology , crustacean , fish <actinopterygii>
Crayfish Orconectes virilis appeared in Newcastle Reservoir, Utah, in the 1970s. Rainbow trout Salmo gairdneri are stocked annually in the reservoir to support a sport fishery. Predation of rainbow trout on crayfish was studied during 1983‐1985. This predation was seasonal, occurring only during June‐December. It was greatest during June‐August, when up to 100% of fish stomachs contained crayfish. Relative sizes of predators and prey helped to limit crayfish consumption by fish, but seasonal behavior and distribution of crayfish also influenced their availability. Crayfish of ingestible sizes occupied the reservoir throughout the year, though rainbow trout did not eat them in winter and early spring. Crayfish were consumed up to a size of 38 mm in carapace length (CL). They grew to a size of 22 mm CL during their first year and attained a maximum size of 60 mm CL. Rainbow trout growth declined after crayfish became abundant in 1979. Crayfish changed the reservoir ecosystem by altering the food web and thereby reducing the energy transfer to rainbow trout. Fish‐stocking rates were cut in half in 1983 and 1984 to improve the growth rate of rainbow trout.