Salish Sea Marine Survival Project

78 Juvenile Salmon in the Salish Sea Beyond estuaries and the nearshore habitats, juvenile salmon are widely distributed in open marine waters. SSMSP research built on existing DFO trawl surveys conducted twice annually, and conducted consistently since 1998. These surveys are the key source of juvenile salmon (and other fishes) data on abundance, distributions, and body conditions over time and space for 20 years! Genetic analyses of Chinook and Coho samples enables researchers to identify the local populations that our samples originated from. Critical new understandings have emerged for Chinook salmon: different populations consistently use different areas of the Strait of Georgia; and Chinook present in late summer differ from the early summer and are dominated by the South Thompson summer Chinook population. Further, one of Canada's largest Chinook populations (the Harrison River Fall white Chinook) rear in upper Puget Sound more than in the Strait of Georgia. Coho salmon are more broadly distributed through the Strait of Georgia and analyses are revealing the importance of their early marine survival as the determinate of subsequent adult returns. For both Chinook and Coho salmon, these observations are consistent with statistical analyses of coded-wire tagging on hatchery fish that pre-date these DNA results. An important observation has been that Coho salmon have recently been remaining within the Strait through fall and winter and have been in excellent body condition during these years. Of the other fishes, Pacific Herring are by-far the dominant species during these surveys. RESEARCH TOPIC OUTCOMES Nearshore Habitat Restoration and Research (continued) Focus was on mapping changes over time and assessment of anth- ropogenic impacts on biodiversity and resilience of these habitats; studies to assess the importance of nearshore habitat connectivity; as well as assessments of the environmental requirements for successful restoration. Novel SSMSP projects included the utility of satellite imagery, aerial imagery, and drones to examine changes in the extent of bull kelp and eelgrass beds; use of stable isotopes to examine source of salmon diet; examination of otoliths to determine loss of Chinook life history variants in degraded estuaries; and other studies to examine thermal tolerance in kelp, as well as the effects of temperature stress and herbivore grazing as limitations to bull kelp distribution. Globally, seagrass ecosystems are declining in area. SSMSP researchers have been assessing the overall decline or degradation of eelgrass nursery areas in the Strait of Georgia and found that estuary degradation is related to anchorage scour, shoreline activities ((boats, docks, log booms and armouring), development, alterations and contaminants. Results suggest an overall deterioration of coastal environmental health in the Salish Sea due to increased use of the coastal zone as well as declines in water quality due to urbanization. Studies showed evidence of decreased species richness and increasing simplicity of eelgrass fish communities in highly disturbed regions (e.g. sites within Fraser Estuary, Comox Estuary, southern Vancouver Island). In the Cowichan River, the estuary was particularly important to smaller fry as compared to stream-rearing Chinook that left the river at a larger size. High mortality rates for river-reared smolts in some years suggest that estuary-reared counterparts could have a survival advantage in years of low flow, and may be an important component of annual Chinook production. Kelp shows decreased reproductive activity when waters are warm, and rising ocean temperatures are thought to be a major contributor to kelp declines. Eelgrass restoration activities have been successful in many areas of the Strait, but are hampered due to many anthropogenic impacts in estuaries as well as climate change impacts.

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