An interdisciplinary investigation of shifting baselines in the socio-ecological system of Pacific herring and Salish Sea peoples

Baselines of ecosystem health are often estimated from relatively recent observations of systems that have already been degraded by human activities. Pacific herring (Clupea pallasi) might be an example of ‘shifting baselines’, as commercial fishing depleted stocks before the onset of biomass estimates. Here, we present an interdisciplinary approach to reconstruct population diversity and human use of Pacific herring before industrial fishing. Specifically, we (i) synthesize local ecological knowledge to evaluate the cultural significance and abundance trends of herring, (ii) investigate the genetic structure of extant herring populations, and (iii) quantify relative contributions of different populations to pre-contact diets by analyzing DNA from archaeological herring bones. Interview data suggested that herring were more abundant in the mid-20^th century than today and were an important source of food and bait. There was also evidence of shifting baselines in the perception of ecosystem health among fishers. Preliminary DNA data confirmed genetic differentiation among extant herring populations and demonstrated the feasibility of the ancient DNA approach.