Quantifying habitat correlates for salmon in coastal waters

Marine survival of Pacific salmon is highly influenced by the physical and biological environment in coastal waters.  Yet, predictions of salmon survival are often tenuous due to the dynamic aspect of the coastal environment.  Moreover, managing a migratory species like Pacific salmon is made more difficult by the transient nature of their habitat use.  Expanding on previous analyses, we used logistic regression to characterize habitats that are correlated with the presence of salmon to improve our understanding of how salmon respond to local cues during migration.  We used presence/absence data from an ongoing surface trawl survey (1998 through 2009; over 1300 trawls) along Washington and Oregon coastlines to model Chinook and coho salmon habitat correlates.  Input variables included water depth, satellite-derived chlorophyll a concentration, and water temperature.  To better estimate the true correlation between these variables and salmon presence, we also included time of year and spatial location in the model, which are known to influence the probability of catching salmon.  For Chinook and coho, all three environmental variables were highly significant in predicting the probability of salmon presence.  Final model selection was performed using AIC.