Portfolio simplification arising from a century of change in salmon population diversity and artificial production

1. Population and life-history diversity can buffer species from environmental variability and contribute to long-term stability through differing responses to varying conditions akin to the stabilizing effect of asset diversity on financial portfolios. While it is well known that many salmon populations have declined in abundance over the last century, we understand less about how different dimensions of diversity may have shifted. Specifically, how has diminished wild abundance and increased artificial production (i.e., enhancement) changed portfolios of salmon populations, and how might such change influence fisheries and ecosystems?
2. We apply modern genetic tools to century-old sockeye salmon (Oncorhynchus nerka) scales from Canada’s Skeena River watershed to (i) reconstruct historical abundance and age-trait data for 1913–1947 to compare with recent information, (ii) quantify changes in population and life-history diversity and the role of enhancement in population dynamics, and ..., Generated from fish scales collected in commercial fisheries during 1913–1947 and the skeena tyee test fishery 1973–2016, genetically assigned to population.,