Research Document - 2008/075

Biological Risk Assessment for Smallmouth bass (Micropterus dolomieu) and Largemouth bass (Micropterus salmoides) in British Columbia

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

Abstract

We performed a qualitative risk assessment of the ecological and genetic impacts of the non-native smallmouth bass (Micropterus dolomieu) and largemouth bass(Micropterus salmoides), and their parasites, pathogens, and fellow travelers to native ecosystems in British Columbia. The basses are widely distributed in North America, and have been introduced into southern British Columbia. They were originally introduced into BC by government agencies, although their recent spread into new water bodies is by unauthorized means, mainly by angling enthusiasts. Smallmouth and largemouth bass are adaptable voracious littoral zone predators. Once they establish themselves in water bodies they present a high risk to native biota and often cause the extirpation of native fish species, primarily minnows. The risk is very high in small lakes and lower in larger water bodies which have less of the preferred habitat for the basses. The probability of widespread establishment once they have arrived in a water body was rated high to very high for five of the eight regions in BC. Because there are no members of the Centrarchid family native to BC, the potential genetic impact of establishment of the basses is very low. There were few published papers to inform our assessment of the potential impact of parasites, pathogens, and fellow travelers to native ecosystems in BC, however the risks were considered low.

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