Behavioural ecology and distribution of Pacific salmon in a fjord estuary of the Salish Sea

Evaluations of habitat use and the functions of specific habitats in an organism’s life history can help identify potential survival bottlenecks and guide the development of habitat-based conservation measures. Using acoustic telemetry, I investigated the effect of biological and environmental factors on the residence of sub-yearling Chinook Salmon Oncorhynchus tshawytscha in a fjord estuary in British Columbia. Wild Chinook Salmon (n=49; 67-95 mm) were experimentally released into the estuary of which 36 exited successfully. The median residence duration for the fish I released was 11.2 days (95% CI 6.5 -15.5). Using model selection and time-to-event analysis, I found tide direction and salinity to be important factors influencing when fish left the estuary. While in the estuary, fish displayed either direct or indirect migration patterns. Binomial generalized linear models were used to evaluate the association between intrinsic factors and the probability of a fish making direct movements. In this analysis, faster freshwater growth increased the probability of a fish making direct movements out of the estuary. This study indicates this estuary to be a stop-over habitat for larger sub-yearlings. The results of this study also suggest migration phenology and habitat use are both partially shaped by intrinsic factors in sub-yearling Chinook Salmon. In a second experiment, I modelled the spatial distribution of juvenile salmon (O. kisutch, O. keta, O. tshawytscha) and flatfish (Platichthys stellatus) in a fjord estuary as a function of habitat conditions. Fish were captured bi-weekly in channel and beach habitats (n=20) at the North end of Howe Sound. A spatial generalized linear model (sdmTMB) was used to elucidate associations between catch and habitat factors. Both environmental and structural habitat factors were included as predictors. I found most associations between catch and the variables included in the analysis to be weak. The results of the two studies in this thesis indicate environmental conditions to have weak and uncertain effects on the residence duration and distribution of juvenile salmon in the fjord estuary studied, which suggests juvenile salmon are able to exploit a range of habitats and tolerate variable environmental conditions.Forestry, Faculty ofGraduat