Evaluating the effect of residency on marine survival


Investigators: Lance Campbell and Sandie O’Neill (Washington Department of Fish and Wildlife), Josh Chamberlin (NOAA)

Extended residence in the Salish Sea may negatively impact overall marine survival of salmon in the region, especially for Chinook and coho. Increased contaminant load, delayed competition for limited and seasonal prey, and increased predation by local marine mammal populations may all contribute to reduced survival and warrant further research. This study examines what  proportions of Chinook and coho display residency, whether the proportion of residents has changed over time, and whether there is a correlation between the proportion of residents and marine survival.

Recent results indicate that resident Chinook and coho salmon have elevated levels of PBTs and distinct chemical fingerprints as a consequence of their feeding within the Puget Sound food web. However, PBT chemical fingerprints are expensive and less feasible to apply to long-term sample sets such as otoliths and scales. Researchers use PBT contaminant concentrations of Chinook and populations assumed to be resident and nonresident (based on capture location and timing) to determine whether a distinct chemical signal indicative of residency can be developed for otoliths or via carbon isotopes. Analyzing existing otolith or scale sample sets from adult spawners allows researchers to evaluate the proportion of residents that contributed to the spawning population in low vs. high years of marine survival.