Recovery potential assessment for white sturgeon (Acipenser transmontanus) upper Fraser designatable unit / E. Smyth ... [et al.].: Fs70-5/2016-071E-PDF

"We assessed the recovery potential for the Upper Fraser White Sturgeon DU by examining the current population status, potential threats, and possible results of management strategies. Within the Upper Fraser DU, there are three distinct groups (or sub-DUs): the Mid-Fraser group, the Upper Fraser group, and the Nechako River group. Twelve threats to White Sturgeon in the Fraser River are discussed. Abiotic threats include loss of habitat, habitat fragmentation, altered hydrograph, pollution, reduced turbidity, fishing effects, and altered thermal regime. Biotic threats include small population size effects, hatchery and aquaculture, reduced or altered food supply, change in ecological community, and disease. Metapopulation models were designed to evaluate the effect of changes to mortality or habitat productivity on the abundance of the three groups. The models also consider uncertainty in life history parameters and exchange among groups. Relatively small changes to human-induced mortality or habitat productivity had substantial effects on the abundance of sturgeon in the Mid-Fraser and Upper Fraser, given the parameter and modeling assumptions. Losses here were mitigated by the introduction of individuals from the Nechako group, given the model structure and exchange rate assumptions. Changes to human-induced mortality or habitat productivity had little effect on the Nechako group meeting its abundance target; however, this was dependent on a large number of fish annually stocked and a high survival rate of stocked fish"--Abstract.

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