Quantifying survival of age-2 Chilko Lake sockeye salmon during the first 50 days of migration

We used acoustic telemetry to investigate survival of age-2 sockeye salmon (Oncorhynchus nerka) as they emigrated from Chilko Lake, British Columbia, Canada, to northeastern Vancouver Island (NEVI) from 2010 to 2014. We built on our previously reported results by including an additional year of data and by converting survival estimates into rates (distance and time) to compare across disproportionate habitats. We also refined our survival estimates by including individual covariates in our survival models and by re-investigating the detection efficiency of the final detection site. There was a tag burden effect in 2012 and a body size effect in 2013. Excluding 2010, survival during the 35-to 47-day migration to NEVI (range of annual mean travel time; 1044 km) ranged between 8% and 14%. Weekly survival rate (S·week −1 ) during downstream migration to the Fraser River estuary, through the central Strait of Georgia (CSOG), and NEVI was 25%–46%, 75%–90%, and 34%–64%, respectively. In addition to marked losses in freshwater tributaries, sockeye also experienced high losses north of the CSOG consistent with earlier results for Cultus Lake sockeye.