Salish Sea Marine Survival Project

56 0 20 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016 2018 SEPTEMBER CPUE (catch/hr) 40 60 80 100 No Survey -30 -20 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016 COHO SIZES SEPTEMBER -10 0 20 30 10 DEVIATION FROM MEAN (mm) Figure 5. CPUE for juvenile Coho Salmon in the Strait of Georgia in September. Figure 6. Size of Coho juveniles in the Strait of Georgia in September. Positive deviations from the mean (for 1998-2016) indicate larger fish. Juveniles have been generally larger by September since 2013. Figure provided by Chrys Neville, DFO. NEXT STEPS There are a number of important questions this study is working to answer: Are growth patterns, health status, or condition of juveniles rearing in different regions significantly different? How do these conditions change across years with different oceanographic conditions? Can we identify the fish that will survive based on their early marine growth, distribution or condition? If fish are not changing distribution patterns based on oceanographic conditions how does this impact survival? What implications does this have on hatchery production or other actions intended to increase salmon survival and availability to sport and commercial fisheries? Analyses for this project are ongoing. The DFO trawl survey provides one of the best long-term data series for juvenile Coho and Chinook stock distributions, growth, survival and state of health as well as valued and additional infor- mation on the Strait of Georgia marine ecosystem. We suggest that it is crucial that DFO continues this program and makes these data more available in the future. An analysis of historical Salish Sea Chinook survival data indicated that survival rates varied significantly between populations, but were similar for populations derived from closely-located river systems. This would make intuitive sense given that these populations were likely rearing in very similar areas in the Strait, and experiencing comparable oceanographic conditions. A surprise in the results were the low numbers of Harrison/ Chilliwack Chinook Salmon captured in the Canadian survey area. This stock is the dominant stock of Chinook Salmon in the Fraser River and would be expected to represent about 40% of the Chinook captured, however, it represented only about 5% of the catch. Associated surveys in the US San Juan Islands and in Puget Sound indicate that as juveniles, Chinook rear in the southern Strait of Georgia (US zone) and in Puget Sound. Coho The CPUE of Coho Salmon has increased since 2009 (Figure 5). The size and condition of the juveniles has also increased. Along with this change has been a change in the residency behaviour of Coho Salmon in the Strait. After the early 1990s Coho Salmon no longer appeared to stay in the Strait over winter. Beginning in about 2013, Coho Salmon (age 2+ years) were found to be present in the Strait of Georgia in the late spring when the recreational fishery opened. This was suggested to be due either to Coho overwintering in the Strait or returning to the Strait in the late winter. In 2017/2018 some Coho Salmon remained in the Strait of Georgia over their first marine winter. This information was gathered by the hook and line efforts of a local SOG sport fishing/research group called the "Avid Anglers" who fish year-round. It is the first time in over 20 years that there was an abundance of Coho Salmon in the Strait of Georgia in the winter. It may indicate that the behaviour we saw in the 1970s and 1980s is returning and that there may possi- bly be more food for the juveniles in the Strait of Georgia. Although it is difficult to determine if there is higher food availability for Coho in the Strait, studies are examining the early marine growth of these Coho Salmon to determine if they are growing better. Field results indicate that since 2013, the Coho juveniles in their first ocean year in September have been larger each year (Figure 6). The fish that were in the Strait in February 2018 were 30-35 cm (12-14 inches), or about the size of the Bluebacks in the 1970s.

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