Analyzing tradeoffs between the threat of invasion by brook trout and effects of intentional isolation for native westslope cutthroat trout

Abstract

Native fishes often face simultaneous threats from habitat fragmentation and invasion by nonnative trout. Unfortunately, management actions to address one may create or exacerbate the other. A consistent decision process would include a systematic analysis of when and where intentional use or removal of barriers is most appropriate. We developed a Bayesian belief network (BBN) as a tool for such analyses. We focused on native westslope cutthroat trout (Oncorhynchus clarkii lewisi) and nonnative brook trout (Salvelinus fontinalis). We considered the environmental factors influencing them, their potential interactions, and the effects of isolation on the persistence of local cutthroat trout populations. The tradeoffs between isolation and invasion were strongly influenced by the size and quality of the stream network to be isolated and existing demographic linkages within and among populations. A strength of our approach was that it captured interactions where effects would otherwise difficult to visualize. The model can be used to conduct site-level analysis of barrier management relative to other possible conservation actions, such as habitat improvement or angling restrictions, and to help prioritize actions among streams. By eliciting precise definitions of conservation priorities, the model can also help clarify management objectives and facilitate communication among biologists, managers, and the public.

Citation

Peterson, Douglas P.; Rieman, Bruce E.; Dunham, Jason B.; Fausch, Kurt D.; Young, Michael K. 2007. Analyzing tradeoffs between the threat of invasion by brook trout and effects of intentional isolation for native westslope cutthroat trout. In: Carline, R.F.; LoSapio, C., eds. 2007. Sustaining wild trout in a changing world; proceedings of Wild Trout IX symposium; 2007 October 9-12; West Yellowstone, Montana: 51-57.