Isotope analysis of bone from archaeological middens and sediments in salmon spawning lakes has the potential to yield information on changing trophic dynamics and ocean productivity through time and to relate these to cultural change and human subsistence in coastal areas. We investigated fluctuations in the d15N and d13C of six marine species over the past 4,500 years (Steller sea lion, harbor seal, northern fur seal, sea otter, Pacific cod, and salmon) of samples collected from Sanak Island, AK in the Northeastern Pacific. Of the marine mammals, sea otters had the highest mean d13C (-11.9 ±0.7‰) and lowest d15N (14.5 ±1.4‰) while northern fur seal had the lowest d13C (-13.6 ±1.4‰), and Steller sea lions had the highest d15N (18.4 ±1.4‰). Cod reflect a demersal, near-shore habitat (-12.5 ± 0.9‰ d13C, 16.1 ± 1.4‰ d15N) while salmon isotope ratios demonstrate an open-ocean habitat and lower trophic position (-15.2 ± 1.4‰ d13C, 11.5 ± 1.7‰ d15N). There is a significant difference in mean d13C between modern (1950 – 2000 AD) and prehistoric sea lions, sea otters, harbor seals and salmon. When comparing six prehistoric time periods salmon had a statistically significant difference in d13C while otters had a difference in d15N. Levels of salmon derived nutrients inferred from d15N in lake cores collected on Sanak, suggest increases in salmon populations since the mid-Holocene. The paleo-data suggest that our current understanding of climate regimes and their effects on northeast Pacific ecosystems may not be extensive enough to explain past regime and ecosystem change.
