| Summary: | Several studies have suggested that early ocean growth rate of juvenile salmon relates to subsequent adult returns. A corollary is the abundance and nutritive quality of prey available will dictate growth rates and thus also relate to adult returns. The Salish Sea Marine Salmon Survival Project was organized to help understand why “Chinook, coho, and steelhead have experienced tenfold declines in survival during the marine phase of their lifecycle, and their total abundance remains well below what it was 30 years ago.” The first key hypothesis of the Salish Sea Marine Survival Project is: “Bottom-up processes that drive juvenile Chinook, coho and forage fish prey availability have changed and his is limiting salmon growth and survival.” Coincidently the Pacific Salmon Commission Southern Fund supported a study of growth for juvenile salmon in the Strait of Georgia, using measures of the hormone IGF1. IGF1 levels have been shown to be well correlated with feeding and growth in juvenile salmon. Samples were obtained on the DFO June juvenile salmon survey 2012 - 2015. The study revealed both spatial and inter-annual differences in growth for all species assessed (coho, chinook, chum and pink salmon). As part of the Salish Sea Marine Survival Project, zooplankton abundances and species composition are being monitored in the Salish Sea. In this study, we compare the spatial and temporal patterns of the zooplankton in the Salish Sea with the patterns of IGF1 for several species of juvenile Pacific salmon. We ask whether ‘hotspots’ for plankton are concurrent with ‘hotspots’ for juvenile salmon growth, and whether there is a correlation between the occurrence of the ‘right’ kind of plankton and salmon growth. This analysis could identify locations in the Salish Sea which are important for growth and survival of salmon, and therefore important locations for enhanced management or protection.
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