Research Document 2018/021

Recovery Potential Modelling of Rainbow Trout, Oncorhynchus mykiss (Athabasca River Populations)

By Caskenette, A.L., and Koops M.A.

Abstract

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) has assessed the Athabasca River populations of Rainbow Trout (Oncorhynchus mykiss) as Endangered in Canada. Here we present population modelling in support of the recovery potential assessment of the species. Results include a sensitivity analysis, determination of allowable harm, and minimum viable population estimates to inform recovery targets for population abundance and required habitat. The analyses demonstrate that the dynamics of Rainbow Trout populations are particularly sensitive to perturbations that affect survival of immature individuals. Harm to these portions of the life cycle should be minimized to avoid jeopardizing the survival and future recovery of Athabasca River Rainbow Trout populations. To achieve demographic sustainability (i.e., a self-sustaining population over the long term) under conditions with a 15% chance of catastrophic mortality event per generation and a quasi-extinction threshold of 50 adults at 1% probability of extinction, with 100% of the population exhibiting a stream resident life-history, the adult Rainbow Trout abundance needs to be at least 270,425 adult Rainbow Trout, requiring 14,477 ha of suitable habitat. Estimates for alternative risk scenarios are highly sensitive to the extinction threshold, the probability of catastrophic mortality, and the ratio of individuals from river migrant and stream resident life-history types in the population.

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