Analysis of trade-offs between threats of invasion by nonnative brook trout (Salvelinus fontinalis) and intentional isolation for native westslope cutthroat trout (Oncorhynchus clarkii lewisi)

Abstract

Native salmonid fishes often face simultaneous threats from habitat fragmentation and invasion by nonnative trout species. 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 the most appropriate action. We developed a Bayesian belief network as a tool for such analyses. We focused on native westslope cutthroat trout (Oncorhynchus clarkii lewisi) and nonnative brook trout (Salvelinus fontinalis) and considered the environmental factors influencing both species, their potential interactions, and the effects of isolation on the persistence of local cutthroat trout populations. The trade-offs between isolation and invasion were strongly influenced by size and habitat quality of the stream network to be isolated and existing demographic linkages within and among populations. An application of the model in several sites in western Montana (USA) showed the process could help clarify management objectives and options and prioritize conservation actions among streams. The approach can also facilitate communication among parties concerned with native salmonids, nonnative fish invasions, barriers and intentional isolation, and management of the associated habitats and populations.Résumé : Les poissons salmonidés indigènes font souvent face simultanément à une double menace représentée par la fragmentation des habitats et l'invasion de salmonidés non indigènes. Malheureusement, les aménagements faits pour régler un de ces problèmes peuvent faire surgir ou exacerber le second. Un processus de décision cohérent devrait inclure une analyse systématique du moment et de l'endroit les plus appropriés pour l'érection ou le retrait de barriè-res. Nous avons mis au point un réseau de croyance bayésien pour servir d'outil pour ces analyses. Nous nous sommes intéressés spécifiquement à la truite fardée (Oncorhynchus clarkii lewisi) indigène du versant occidental et à l'omble de fontaine (Salvelinus fontinalis) non indigène; nous avons tenu compte des facteurs du milieu qui influencent les deux espèces, de leurs interactions potentielles et des effets de l'isolement sur la persistance des populations locales de truites fardées. Les compromis entre l'isolement et l'invasion sont fortement influencés par la taille et la qualité des habitats du réseau de cours d'eau à isoler, ainsi que par les liens démographiques établis à l'intérieur des populations et entre elles. L'utilisation du modèle dans plusieurs sites de l'ouest du Montana (É.-U.) montre que le processus peut servir à éclaircir les objectifs et les options de l'aménagement et à établir les priorités des initiatives de conservation dans les différents cours d'eau. Cette méthode peut aussi faciliter la communication entre les divers intervenants préoc-cupés par les salmonidés indigènes, les invasions de poissons non indigènes, les barrières et l'isolement délibéré, ainsi que par l'aménagement des habitats et des populations ...

Wildfire may increase habitat quality for spring Chinook salmon in the Wenatchee River subbasin, WA, USA

“…We found Bayesian network analysis to be a good fit, and used Netica software version 4.16 (Norsys Software Corp., Vancouver, British Columbia). Bayesian network analysis has been used successfully to facilitate prioritization of habitat for conservation planning in terrestrial (Marcot et al, 2006) and aquatic settings (Rieman et al, 2001;Peterson et al, 2008;Borsuk et al, 2012;Falke et al, 2015). In a Bayesian network modeling environment, conditional probability tables (CPT) represent the probability of different outcomes based on prior knowledge (Marcot et al, 2006), and are a crucial link for both modeling and transparency.…”

A Fine-scale Assessment of Using Barriers to Conserve Native Stream Salmonids: A Case Study in Akokala Creek, Glacier National Park, USA

“…Increasingly, isolation management is being used to protect headwater populations of cutthroat trout in western North America [8,10,11]. The westslope cutthroat trout is native to the upper Columbia, upper Missouri, and South Saskatchewan River drainages in western North America and has the largest range of the 12 extant subspecies of cutthroat trout in North America [5].…”

“…In western North America, the distributions and abundances of many native trout populations have declined population sizes are inherently vulnerable to demographic and genetic stochasticity [9]. Consequently, resource managers are often faced with the decision of choosing isolation management strategies to prevent upstream movements of nonnative fishes against maintaining or restoring connectivity to conserve native populations [10][11][12][13]. This management paradigm is faced by resource managers interested in protecting critical populations and species adaptations across the landscape, but stream-specific data to inform the decision making process when streams are chosen for isolation management are limited in most situations.…”

A Review of Bayesian Networks as a Participatory Modeling Approach in Support of Sustainable Environmental Management

“…In ten cases, information from more detailed numerical models was integrated into the BN (Table A1). Peterson et al (2008) developed in total three BNs with the same network structure but with different CPTs, with one reflecting only expert knowledge. They compared the performance of the models and concluded that the outcomes of the three BNs were consistent.…”