|| Crustaceans (Phylum Arthropoda,
Class Crustacea) are found in marine, brackish and fresh waters. Common methods
of introduction include ballast water discharge, intentional release as forage
for sport fish, and accidental release from aquaculture facilities. Potential
impacts include competition with, and predation on, native species. The opossum
shrimp, Mysis relicta, was first introduced into Kootenay Lake, British
Columbia, in 1949 and was widely stocked as a forage food for sport fish in the
West. It is an opportunistic feeder with both predatorial and filter feeding habits.
Dramatic changes in native zooplankton communities, including species extinctions,
have been observed after opossum shrimp were introduced. After the introduction
of the opossum shrimp into Flathead Lake, Montana, Daphnia longiremis and
Leptodora kindti were reduced to undetectable levels while Diaptomus
ashlandi declined more than 75% from previous levels.