UBC Theses and Dissertations
Influences of parental identity and elevated incubation temperature on the survival, development and early life history traits in sockeye salmon Burt, Jennifer Mary
Pacific salmon experience intense selection pressures during their early development, and offspring survivorship and fitness traits are influenced by both parental and environmental influences. Given that elevated water temperature can critically impact early development, this thesis focuses on how individual spawners within a population influence the variation in offspring responses to thermal stress. The importance of parentage in assessing temperature effects on fish early life history was first examined in a comprehensive literature review. Only 20% of search-identified studies relating to incubation temperature assessed parental influences, but over 90% of those studies reported significant parentally mediated thermal responses. Research gaps in this area included a paucity of studies on offspring physiological traits (11% of studies), performance traits (2%), and on offspring responses beyond endogenous feeding stages (21%), providing impetus for future experiments. A review of the research on intergenerational temperature effects from adult thermal holding studies was also examined. Sockeye salmon were used in a cross-fertilization experiment to test the hypothesis that significant variation in offspring responses to embryonic temperature stress could be explained by parental identity. Using gametes from Weaver Creek spawners, 10 offspring families were replicated and incubated at 12, 14, and 16ºC from fertilization to hatch. Offspring families had substantially different survival responses across the thermal gradient (crossing reaction norms), and post-treatment mortality and offspring size reflected persistent temperature and parental influences. Within temperature treatments, substantial variation in embryonic survival, alevin mass, time-to-hatch, and hatch duration was attributable to family identity, and most traits exhibited significant temperature-family interactions. The same families were reared for three weeks after emergence then subjected to a second experiment assessing swim performance. Swim performance was reduced in fish exposed to the elevated incubation treatments and offspring parentage was found to have a significant effect on fry burst swim time; findings previously undocumented in salmon. Significant temperature-by-family interactions provide further evidence that parental and temperature influences cannot be examined in isolation. In the context of climate change, these findings collectively highlight the importance of family-level variation in influencing future selection within salmonid populations exposed to elevated thermal regimes.
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