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Research Document - 2008/074

Biological Risk Assessment for Northern Pike (Esox lucius), Pumpkinseed (Lepomis gibbosus), and Walleye (Sander vitreus) in British Columbia

By M.J. Bradford, C.P. Tovey
and L-M. Herborg


We conducted a qualitative biological risk assessment for three invasive freshwater fish species, the northern pike (Esox lucius), pumpkinseed (Lepomis gibbosus), and walleye (Sander vitreus) for British Columbia. All three species are native to North America, and pike and walleye are native to northeastern BC. All three species are present in southern BC through a combination of introductions and spread from introduced populations in the United States.

The northern pike currently is found in only a few locations in the Columbia basin. There are many documented cases of it causing extensive impacts to fish fauna through predation when introduced; those impacts are most severe in small lakes and on species found in the littoral. The pumpkinseed is found in many locations in southern BC; its expansion into central and northern BC is likely limited by its preference for warmer water temperatures. Pumpkinseed can be considered a nuisance species; it is not normally piscivorous, but it can reach high densities and be a competitor to native fish and impact benthic communities. Walleye have reached BC as migrants in the Columbia River system from introduced populations in Washington State. Walleye have been documented to prey on salmonids and other fish and may decrease the productivity of native populations.

Consequently, all three species are considered to present high risks to native biota if they spread further in BC. Little is known about the impacts of parasites that introduced fish may bring with them.

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