An Expert Panel Approach to Assessing Potential Effects of Bull Trout Reintroduction on Federally Listed Salmonids in the Clackamas River, Oregon

Abstract

The bull trout Salvelinus confluentus is an apex predator in native fish communities in the western USA and is listed as threatened under the U.S. Endangered Species Act (ESA). Restoration of this species has raised concerns over its potential predatory impacts on native fish fauna. We held a five-person expert panel to help determine potential impacts of reintroducing bull trout into the Clackamas River, northwest Oregon, on the viability of four anadromous salmonid populations that are listed as threatened under the ESA: spring and fall Chinook salmon Oncorhynchus tshawytscha, coho salmon O. kisutch, and winter steelhead O. mykiss. The panel session was rigorously structured and used a modified Delphi process with structured expert elicitation, disclosure, discussion, and brainstorming. Each panelist distributed 100 score points among seven categories of potential bull trout impact (from no impact to very high impact) on extinction probabilities for the anadromous salmonids. Results were provided by individual panelists rather than as a group consensus and were summarized as means and variations in scores to express the panelists' individual uncertainty, variability among the panelists, and expected differences among the affected salmonids. Score results suggested that panelists viewed the potential impact of bull trout as very low or moderately low for spring Chinook salmon, coho salmon, and winter steelhead and mostly none to very low for fall Chinook salmon. Panelists also provided 19 possible monitoring activities and 21 possible management actions for assessing potential impacts and taking remedial action if bull trout are found to have unacceptable adverse effects. Results of the panel were used by the U.S. Fish and Wildlife Service to help craft and execute a plan to reintroduce bull trout into the Clackamas River system under the ESA. This rigorous expert panel process can be used for a wide range of evaluations in situations where empirical data are sparse or ecological interactions are too complex for explicit analytic solution.

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“…This should not be a solo effort; the process typically involves a small working group that collaborates closely with additional stakeholders and domain experts-biologists, scientists, decision makers-who contribute knowledge and peer reviews (Marcot et al 2001(Marcot et al , 2006. Model building can be done through a well-organized series of workshops or panel sessions designed to ensure scientific rigor and elicit expert judgment (Johnson and Weaver 2009;Marcot et al 2012). Biologists without previous experience can consult with decision analysis experts for guidance on how to structure these workshops or find suitable decision analysis methods.…”

Use of expert knowledge to elicit population trends for the koala (Phascolarctos cinereus)

“…Structured expert elicitation has been used to address a broad range of ecological topics (e.g. Grech et al, 2012;Marcot et al, 2012;McDaniels et al, 2012), including potentially dealing with uncertainty in an adaptive management context (Keith et al, 2011). This has led to its increasing recognition as a valid method for capturing and summarizing knowledge and characterizing uncertainty when empirical data on species distributions and abundances are limited or dispersed (Cooke, 2013).…”

Evaluating potential conservation conflicts between two listed species: sea otters and black abalone

“…As the lists of threatened and endangered species grow, there is an increase in the probability of situations in which species that interact as predator and prey are both depleted. Such cases have been explored theoretically and via expert panels, particularly where predator range expansion or recovery actions could threaten prey species (e.g., Chade`s et al 2012, Marcot et al 2012. However, there have been no field-based studies explicitly quantifying relationships between endangered predator and prey populations.…”