Genomic vulnerability of a freshwater salmonid under climate change.

Understanding the adaptive potential of populations and species is pivotal for minimizing the loss of biodiversity in this era of rapid climate change. Adaptive potential has been estimated in various ways, including based on levels of standing genetic variation, presence of potentially beneficial alleles, and/or the severity of environmental change. Kokanee salmon, the non-migratory ecotype of sockeye salmon (), is culturally and economically important and has already been impacted by the effects of climate change.

Tracking wild sockeye salmon smolts to the ocean reveals distinct regions of nocturnal movement and high mortality.

Few estimates of migration rates or descriptions of behavior or survival exist for wild populations of out-migrating Pacific salmon smolts from natal freshwater rearing areas to the ocean. Using acoustic transmitters and fixed receiver arrays across four years (2010-2013), we tracked the migration of > 1850 wild sockeye salmon (Oncorhynchus nerka) smolts from Chilko Lake, British Columbia, to the coastal Pacific Ocean (> 1000 km distance). Cumulative survival to the ocean ranged 3-10% among years, although this may be slightly underestimated due to technical limitations at the final receiver array.

Immune response genes and pathogen presence predict migration survival in wild salmon smolts.

We present the first data to link physiological responses and pathogen presence with subsequent fate during migration of wild salmonid smolts. We tagged and non-lethally sampled gill tissue from sockeye salmon (Oncorhynchus nerka) smolts as they left their nursery lake (Chilko Lake, BC, Canada) to compare gene expression profiles and freshwater pathogen loads with migration success over the first ~1150 km of their migration to the North Pacific Ocean using acoustic telemetry. Fifteen per cent of smolts were never detected again after release, and these fish had gene expression profiles consistent with an immune response to one or more viral pathogens compared with fish that survived their freshwater migration.

Observable impairments predict mortality of captured and released sockeye salmon at various temperatures.

Migrating adult sockeye salmon frequently encounter commercial and recreational fishing gear, from which they may be landed, escape or be intentionally released. In this experiment, migratory adult sockeye salmon were exposed to simulated capture-release in fresh water, including 3 min of exhaustive exercise and 60 s of air exposure at three ecologically relevant water temperatures (13, 16 and 19°C) to understand how thermal and capture-release stressors may interact to increase mortality risk. Water temperature and sex were the factors that best predicted 24 and 48 h survival, with females in the warmest temperature group experiencing the greatest mortality.

Effects of post-capture ventilation assistance and elevated water temperature on sockeye salmon in a simulated capture-and-release experiment.

The live release of wild adult Pacific salmon (Oncorhynchus spp.) following capture is a management tactic often used in commercial, aboriginal, and recreational fisheries. Fisheries capture and handling can be both exhausting and stressful to fish, which can limit their ability to swim and survive after release.

Differences in thermal tolerance among sockeye salmon populations.

Climate change-induced increases in summer water temperature have been associated with elevated mortality of adult sockeye salmon (Oncorhynchus nerka) during river migration. We show that cardiorespiratory physiology varies at the population level among Fraser River sockeye salmon and relates to historical environmental conditions encountered while migrating. Fish from populations with more challenging migratory environments have greater aerobic scope, larger hearts, and better coronary supply.