Chrys Neville

Early Ocean Life History of Harrison River Sockeye Salmon and their Contribution to the Biodiversity of Sockeye Salmon in the Fraser River, British Columbia, Canada

AbstractDuring a study of the early marine survival of Chinook Salmon Oncorhynchus tshawytscha and Coho Salmon O. kisutch in the Strait of Georgia from 1998 to 2010, moderate abundances of juvenile Sockeye Salmon O. nerka were observed to remain in the strait much longer than previously thought. In 2008, DNA stock identification showed that these juveniles were from the Harrison River, a population with a sea-type life history in which juveniles enter the ocean during the year of emergence from the gravel. Using information collected in 1998–2010, we describe the early ocean life and production of Harrison River sea-type Sockeye Salmon. Juveniles entered the Strait of Georgia from the Fraser River over an extended period, with most entering after mid-July—about 8xa0weeks later than lake-type juveniles, which had virtually all left the strait by that time. The September diets of sea-type juveniles were highly selective for hyperiid amphipods, which were not abundant in the zooplankton. Interaction with juven...

Poor Survival of Acoustically-Tagged Juvenile Chinook Salmon in the Strait of Georgia, British Columbia, Canada

AbstractThe collapse of the commercial fishery and the major decline in catches in the recreational fishery for Chinook Salmon Oncorhynchus tshawytscha in the Strait of Georgia since the mid-1990s represents a major economic loss to British Columbia. Early marine residence is critical for survival of Chinook Salmon, but measuring the amount of mortality has been difficult. Acoustic tags can be used to measure marine mortality and study migratory behavior. We surgically implanted 278 juvenile Chinook Salmon with acoustic tags to monitor when and how many tagged fish moved out of the Strait of Georgia. Only eight tagged fish were detected leaving the Strait of Georgia, indicating that there could have been substantial mortality of the tagged juvenile Chinook Salmon within the strait. Tagging mortality was minimal, and the detection of tags was shown not to be a major source of error in this study. A major change in population structure between the spring and fall tagging periods meant that it was unlikely t...

Stock-Specific Size and Migration of Juvenile Coho Salmon in British Columbia and Southeast Alaska Waters

Abstract The variation at 17 microsatellites was analyzed for 5,270 juvenile Coho Salmon Oncorhynchus kisutch obtained from coastal British Columbia and Gulf of Alaska surveys during 1998–2012. A 270-population baseline was used to determine the individual identifications of the fish sampled, with individuals being identified to 22 stocks of origin. Columbia River and Washington juveniles were consistently larger than those from British Columbia and Alaska. During June, the larger individuals within a stock were observed in more northerly locations. There was a relationship between the timing of northward migration and juvenile body size, with larger individuals migrating earlier than smaller individuals from the same stocks. Stock composition was more diverse in the northern sampling regions than in those in southern British Columbia. There was only a modest change in stock composition between fall and winter samples in both the Strait of Georgia and west coast of Vancouver Island sampling regions, indicating that juvenile migration had largely been completed by the fall. There was a wide divergence among stocks in juvenile size and dispersion among sampling locations.

Is There Evidence for Biologically Significant Size-Selective Mortality of Coho Salmon During the First Winter of Marine Residence?

AbstractWe examined whether individual Coho Salmon Oncorhynchus kisutch in southern British Columbia had to achieve a sufficient size (“critical size”) by the end of the first marine summer to be able to survive through the ensuing fall and winter. Descriptive statistics of seasonal weight distributions were determined. The expected body weight of an individual sampled in one season was projected to the next season with a growth equation tested on Pink Salmon O. gorbuscha. Projected weight frequencies were then compared with observed weight frequencies in the next season to evaluate whether it was necessary to invoke size-selective mortality to explain the observed weight frequencies in the next season. Based on estimated growth between July and September, a maximum of 9% of the stock in the Strait of Georgia may have been subjected to size-selective mortality—far lower than the 63–74% mortality estimated in previous studies. Likewise, there was basically no size-selective mortality between September and ...