Environmental and genetic factors affecting physiological performance in salmonids

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Pacific salmon must undergo a remarkable transformation to maintain internal equilibrium as they migrate between fresh- and seawater. The change from stream dwelling parr to migratory smolt is characterized by a complex series of developmental events that prepare fish for entry into seawater. Hormonal changes in response to springtime increases in daylight and temperature stimulate the physiological phenomenon known as smolting. We know considerably less about the physiological changes that occur in maturing adult salmon as they migrate back to freshwater. Among and within species, the mechanisms for maintaining internal salt balance are similar. There is considerable variation, however, in the age, size and timing of migration between seawater and freshwater. This variability in life history traits provides a mechanism for fish to exploit new habitats or respond to rapid changes in their environment that occur naturally or due to human disturbance. The role genetics plays in the physiological adaptations that allow salmon to exploit new, or survive in disturbed habitats, is not well understood. The objective of the proposed research is to compare physiological performance of salmon from divergent geographic regions and examine their growth, development and survival under environmental conditions to which they are naturally adapted. In addition, changes in physical factors will be used to assess performance among different populations. A further approach for these investigations will be to alter the genotype through the creation of families from different populations of salmon and by modifying ploidy. The investigation of environmental, developmental and genetic bases of phenotypic expression is a novel approach to understanding the mechanisms controlling ion balance in salmon. The proposed work will provide insight into the ability of salmonids that differ genetically to respond to changes in the environment. In addition, there are a number of practical applications to this work. Understanding the interactions between genetic and environmental factors will benefit selection of strains for re-establishment of wild runs and for aquaculture production.