Weaving traditional knowledge, historical records and quantitative ecology to illuminate the causes of shellfish declines in Alaska

We investigated the relative roles of natural factors and shoreline harvest leading to recent declines of the black leather chiton (Katharina tunicata) on the outer Kenai Peninsula, Alaska. This intertidal mollusc is a strongly interacting grazer and a culturally important subsistence fisheries resource for Sugpiaq (Chugach Alutiiq) Natives. We took multiple approaches to determine causes of decline; field surveys examined the significant predictors of Katharina density and biomass across 11 sites varying in harvest pressure, and an integrated analysis of archeological faunal remains, historical records, traditional ecological knowledge, and contemporary subsistence invertebrate landings examined changes in subsistence practices through time. We propose that a spatial concentration in shoreline collection pressure through time, increased harvest efficiency, and the serial depletion of alternative marine invertebrate prey have led to intensified per capita predator impacts on Katharina and thus its recent localized decline.