Homeward bound: A population study on Chinook Salmon (Oncorhynchus tshawytscha) in the Capilano River

Abstract

The decline of Pacific salmon populations on the west coast of Canada has been observed for decades. Hatcheries are used as one solution to this issue, however the benefits and detriments of releasing hatchery-grown salmon into the wild are widely debated. We investigated the release and return numbers of Chinook salmon, Oncorhynchus tshawytscha, at the Capilano River Hatchery in North Vancouver, British Columbia. This study focuses on: (1) establishing whether or not there is a declining trend in the number of returning Chinook salmon over the past seven years, and (2) deciphering the survival rate of a population of salmon. Data was collected by counting the returning Chinook salmon over 10 trials of one hour each. We calculated daily average as well as the use of the release and return data of previous years at the Capilano River Hatchery. The returning rate of Chinook salmon over the past seven years displayed a declining trend until the input of our data, which may be a result of unaccounted environmental factors, such as river height. The return numbers for the 2010 population of Chinook salmon was less than 1.28% in comparison to the amount of salmon released (98.1%). When comparing 2010-2016 return numbers per year, there was no significant effect on returns (z=0.864, df=6, p=0.3875), but there was a significant effect of both Sea Surface Temperature (SST) (z=2.343, df=6, p=0.0191) and an interaction between year and SST (z=-2.338, df=6, p=0.0194) on return numbers. The benefits of these hatcheries remain unclear and should be further studied.