Research Document - 2010/065

Risk assessment of smallmouth bass (Micropterus dolomieu) introductions to rivers of Gulf Region with special consideration to the Miramichi River (N.B.)

By G. Chaput and D. Caissie

Abstract

This document presents the risk assessment of the possible impact of non-native smallmouth bass (Micropterus dolomieu) on Atlantic salmon (Salmo salar) and the native aquatic ecosystem of the rivers of the DFO Gulf Region. Information in this document includes a summary of smallmouth bass biology and its environmental requirements. The risk assessment consists of two components: (1) estimation of the probability of widespread establishment (defined as the sequence of arrival, survival and reproduction, and spread), and (2) the determination of impact once introduced, in terms of its ecological impacts on existing aquatic communities. A timeframe of ten years was chosen for the risk assessment. The probability of widespread establishment for rivers of Gulf Region, and for the Miramichi River specifically, is considered high with low uncertainty. The impacts of smallmouth bass on the ecosystem and specifically to Atlantic salmon were considered to be different between the lake versus the river environments. For lakes, the overall risk assessment of smallmouth bass is high (i.e. smallmouth bass becomes a dominant component of the food web and causes significant widespread reductions in native biota) with low uncertainty. For the riverine environment, the overall risk is considered moderate (i.e. a measurable decrease in abundance of native populations is likely to occur in some locations with smallmouth bass likely becoming a dominant component of the food web) with high uncertainty. There are no features of smallmouth bass ecology which would be positive for Atlantic salmon survival and production, and any interactions with salmon will either be neutral or most likely negative to salmon.

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