Population Viability Models for Salmon Recovery – An Atlantic Perspective

The Gulf of Maine Distinct Population Segment (GOM DPS) of Atlantic salmon was listed as endangered in 2000.  Eight rivers with extant populations were included in the listed DPS.  In 2009, the DPS was expanded to include all watersheds from the Androscoggin River northward along the Maine coast to the Dennys River.  Population viability models for the GOM DPS have ranged from highly complex stage-structured models applied to the eight rivers in the original 2000 listing, to simple diffusion approximation models applied to the DPS as defined in 2009.  Both types of models have their advantages and disadvantages in terms of modeling system dynamics, computational intensity, data needs, and incorporation of hatchery supplementation.  To better balance the desire for model simplicity while still accounting for the contribution of hatchery origin fish in the estimation of population growth rates, we developed a diffusion approximation model in which results from genetic parentage analysis were used to partition wild and hatchery origin fish.  The model was used to estimate population growth rates and probabilities of extinction with and without stocking of hatchery fish. This model will be useful in ongoing recovery planning of Atlantic salmon when considering the need for continued hatchery supplementation.