Sockeye salmon (Ozette Lake ESU) (Oncorhynchus nerka pop. 2)

In general, sockeye salmon likely exhibit sensitivity to warmer water temperatures (freshwater and sea surface) and increased severity or frequency of winter/spring flood events. Washington State is near the southern extent of the range for sockeye salmon, suggesting that they will be sensitive to increases in water temperature (freshwater and ocean). For example, even at the northern extent of their range in Alaska, sockeye salmon in shallow, non-stratified lakes may be thermally stressed in the summer. In Washington, sockeye generally rear in deep, thermally stratified lakes and can move below the thermocline if surface waters become thermally unsuitable. This suggests that sockeye may be less sensitive to temperature during the freshwater phase of their life history as they are able to behaviorally thermoregulate. Additionally, sockeye may be somewhat more buffered from metabolic stresses associated with warmer water temperatures because lake food webs are generally more productive than that of streams. In general, Pacific salmon survival is positively related to sea surface temperatures (SST) at the northern extent of their distribution, and negatively related at the southern extent. Indeed, recent research suggests that survival rates of sockeye salmon are strongly affected by variations in regional SST during early ocean life, with lower survival rates during years with warm SST anomalies (however the mechanisms driving this trend may be upwelling and marine productivity rather than temperature per se). Increases in ocean and estuarine temperature, increased stratification of the water column, and/or changes in the intensity and timing of coastal upwelling may alter primary and secondary productivity, with potential impacts on growth, productivity, survival, and migrations of salmonids. Sockeye salmon are also likely sensitive to winter flood events that can scour substrates or move gravel and silts to bury embryos. Increased severity of winter floods has been linked to decreased egg-to-fry survival in fall-spawning Pacific salmon of Washington.