A genetic analysis of sex-specific prey consumption in harbor seals (Phoca vitulina) and the implications for commercially important fish species in the Pacific Northwest.

Formerly abundant salmonid, rockfish, and herring species are experiencing population decline in the Salish Sea. To design effective management and recovery strategies, we must understand the population dynamics of these fishes in relation to their predator species: the harbor seal (Phoca vitulina). Given that food consumption in the dimorphic harbor seal is related to body mass, an understanding of prey population dynamics requires a description of sex-specific diet preferences. Genetic barcoding was performed on seal scat to generate diet composition data; qPCR was used to identify zinc finger proteins (ZfX and ZfY) to determine the sex of the individual that deposited each sample. Data were collected from two haul-out sites in 2012-2013 in the Georgia Strait, Canada. At Comox during 2012, male harbor seals (n=82 scats) consumed Pacific Hake (37%), salmon species (26%), and Pacific Herring (13%), whereas females (n=68 scats) consumed Pacific Herring (35%), Pacific Hake (8%), salmon species (8%), Pacific Staghorn Sculpin (7%), and Lingcod (5%). Given that Lingcod and sculpins are salmon predators, similar results following complete analysis would indicate that female harbor seals may improve salmon recovery whereas males may diminish it. Findings also highlight the importance of addressing intra-specific differences to understand community interactions and suggest management strategies