Continuous Study: A population study on Chinook Salmon (Oncorhynchus tshawytscha) in the Capilano River Hatchery

Abstract

Over the past few decades, the population of Chinook salmon has been declining in the Pacific Northwest ecosystem, mostly caused by a combination of increasing demand of Chinook in fisheries, a higher predation pressure, and a decrease in survival and reproductive success due to climate change. This species has long been considered a vital player in the Pacific Northwest ecosystem, so a decline in the population will have several serious effects on other species and the environment. In order to recover the Chinook population, hatcheries were built as an additional source for restocking salmon population. However, the recovery efficiency of hatcheries has long been doubted. In order to find the current salmon population recovery of the Pacific Northwest ecosystem, a continuous study was carried following the same procedure is done by Houwelling et al. last year. Our study focused on 1) whether the increase in the number of returning Chinook last year was an outlier or not, and 2) testing if the population of Chinook salmon is still decreasing in terms of the number of salmon returning to the hatchery. Data was collected by counting the number of Chinook returning over one hour period. By averaging the number of five trails and calculating the estimated total number of returning, we compared this year's estimation with the estimation calculated in the previous study. The result showed an increasing returning number (W = 46, p-value =0.006) compared to the 2017 returning number. Our result showed a significantly greater return number of Chinook salmon in 2018 than the return number the previous study estimated in 2017.