Salish Sea Marine Survival Project

54 Figure 2. The period of early marine survival occurs within the first few months after ocean entry for Coho Salmon. TOTAL MARINE SURVIVAL OCEAN ENTRY EARLY MARINE SURVIVAL May June July Aug Sept Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept Oct JUVENILE SALMON STUDIES IN THE STRAIT OF GEORGIA OBJECTIVES OF STUDY This project directly assesses the bottom-up and physio- logical factors limiting the recruitment of Chinook Salmon and Coho Salmon during their early marine life in the Strait of Georgia (SOG). The project is divided into two specific components: 1. A cohort analysis to determine which segment of the population survive the early marine residency period; and 2. An analysis to determine how ocean conditions affect the growth and bioenergetics of juvenile Chinook and Coho. In order to determine whether or not there is a specific component of the population that disappears over time during their first year at sea, salmon smolts are collected as they leave freshwater and subsequently in the marine environment by the DFO trawl survey (Figure 1). Coho and Chinook (both hatchery and wild) were sampled in the Cowichan, and around the Qualicum and Puntledge rivers and the lower Fraser River, as both juveniles and adults. Researchers compare characteristics of adults to those in juveniles to determine those important to their survival. These studies examine the relationships between ocean entry time and size, growth, bioenergetics, diet, fatty acids (in both zooplankton prey and juvenile salmon), presence/ absence of competitors and presence of microbes and early marine survival. Early marine survival is the survival of salmon over the first few months after entry into the Strait of Georgia from their natal rivers, and is depicted in Figure 2. Figure 1. The DFO Trawl Survey 1998-present. Figures 1 through 4 provided by Chrys Neville, DFO. QUESTIONS ADDRESSED DATA CONCLUSIONS Where and why do juvenile Chinook and Coho die in the Strait? What are the characteristics of the survivors? Is there a relationship between early marine growth and survival or residency? Can this mortality be mitigated? DFO Juvenile salmon Trawl Survey 1998-present in Strait of Georgia in June and September. Puget Sound also surveyed in some years. 3 years of freshwater juvenile sampling on Vancouver Island and Fraser River, beach and purse seining in Cowichan Bay and purse seining off Big Qualicum River. Species identification and enumera- tion. Biological data, DNA processing, CWT/fin clip/PIT tag tracking, condition, diet, energy density and otoliths/scales for age and growth analysis. Adult returns in east coast Vancouver Island and selected Fraser River stocks sampled for otoliths and scales. Chinook have stock specific areas for rearing during their residence in the Strait of Georgia over the first marine summer. This may account for similar survival patterns for populations from proximal river systems. Coho abundance in the Strait and early marine survival have been increasing since 2009. The condition of juvenile Coho and Chinook as they enter their first marine winter is related to subsequent survival. Some Coho Salmon are remaining resident in the Strait of Georgia similar to pre-1993. This may be related to their early marine growth and condition in the fall. • 1998-present trawl surveys on standardized track line in the Strait of Georgia to sample ocean age 0 Pacific Salmon • Conducted 2 times/year – late June and September • Surface to 60m • ~80-100 sets/survey

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