Behavioural physiology and fitness of anadromous migrating fish

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The homeward spawning migration of adult anadromous Pacific salmon (Oncorhynchus spp.) is energetically expensive and physiologically stressful. Fish stop feeding days to weeks before entering freshwater from the ocean and commit over half, and often much more, of energy reserves to reach spawning areas. Initially low energy, or elevated levels of stress, metabolic dysfunction, disease, or extreme environments (e.g. high river temperatures or discharge), may result in migration mortality or impaired spawning. Populations vary greatly in run timing into freshwater, migration distance and elevation; hence populations encounter different coastal and river conditions. Populations vary considerably in energy use, fecundity, migration survival and spawning success. And, some are exposed to more extreme environments and much higher levels of exploitation and associated higher levels of predator and human induced injury than others. Pacific salmon populations are thus ideal for examining the fitness consequences on mature and rapidly senescing adult animals of migration experiences and carry-over effects to offspring. In general, the role of environmental variability, and that of adult condition before, during and after the migration, to the reproductive success of individuals is poorly understood. ****Our long-term objective is to establish a broader understanding of the linkages among behaviour, physiology, pathogen loads and disease of migrating adult Pacific salmon in terms of how these influence reproductive success and fitness. Our work is conducted in the Fraser River watershed BC, the largest producer of wild salmon in Canada. We study sockeye, the most commercially valuable and second most abundant Pacific salmon species and pink salmon, the most abundant species. We will conduct large experiments and use tissue biopsy and genomic approaches to investigate how various proxies of fitness in Pacific salmon are influenced by: I) experimental variance in migration temperatures, wounding and pathogens experienced by adults, II) natural variance in the migration environment experienced by adults, and III) differences among individuals in their physiological condition before/after migration. We will compare I to III among populations and species. In this research we will use different measures of eggs, sperm, embryos, fry, and adult attributes as proxies for fitness' consequences and relate these to migration environment and migrant physiological state. There is considerable inter-annual variability in production of juvenile salmon which cannot be explained by simple considerations of variability in number of spawners, so other factors must be involved. Our results will highlight the importance of the quality, condition and migration experience of adult spawners and provide a mechanistic understanding of intergenerational consequences and carry-over effects. **