Salish Sea Marine Survival Project

29 Figure 5. Heron predating on juvenile Chinook in the Cowichan River- herons prefer to forage in shallow waters, less than 25cm depth and foraging success declines rapidly with deeper waters. Photo from BCCF. There was a great deal of concern that these conditions would result in widespread salmon recruitment failures but this did not appear to occur. Impacts to Pacific Salmon have been interesting and complex. Unusually high winter flows and/or temperatures in freshwater systems led to variable impacts, while the subsequent summer droughts combined with record breaking summer temperatures resulted in widespread losses of summer migrating salmon adults and rearing juveniles for many populations. Summer droughts also led to high mortalities for "summer- run" adult sockeye returning to spawning grounds in the Okanagan River (>90% en route mortality), Vancouver Island's Sproat River (hundreds of pre-spawn losses) and the Fraser River (various populations exhibiting 20-50% pre-spawn losses). During SSMSP, we saw very high losses of Cowichan Chinook in-river, likely associated with the low spring flows and easier access for herons and other predators. We also saw negative impacts to kelp populations in the Strait, as temperatures rose well above optimum temperatures for kelp reproduction in many areas. On the positive side, Coho are showing increased resi- dency in the Strait of Georgia (as evidenced by winter catches by a citizen science group, the Avid Anglers), something that has not been seen since the 1990s. Another unexpected result was the increase in size of Coho juveniles in the Strait, which have been much larger than average. So despite increased temperatures, condi- tions in the Strait have been conducive to high growth rates and we believe resulted in higher residency rates. Chinook have also shown high growth rates and have been in good condition, as have all other salmon species and herring. Chinook Salmon appear to show consistent differences in distributions that likely result in different stocks experiencing different environmental and growth conditions. Additionally, there has been a large increase in abundance of Northern Anchovy in the Strait of Georgia. The occur- rence of these fish in very large numbers in the Strait is unique in the 18-year history of the DFO trawl survey. Adult anchovy prefer to spawn in water temperatures that range from 13°-18° C and most reside in warmer Pacific waters. Larval anchovy have been observed in the diets of Coho and Chinook Salmon, and larger juveniles and adults may also provide an alternative prey source for seals and other predators, possibly lessening negative impacts on salmonids and herring. Large catches of multiple age classes of anchovy were encountered in the southern Strait of Georgia in both summer and fall DFO trawl surveys, providing evidence that this species is successfully reproducing in the Strait. Figure 6. Chinook Salmon have stock specific distributions through the early marine period with over 60% of a stock remaining within these regions. They appear to remain in these areas regardless of the ocean conditions. It is likely that feeding and growth vary greatly depending on the particular conditions experienced in these rearing areas. Figure provided by Chrys Neville, DFO.

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