Recent Trend in Variability of Chum Salmon Stock and its Potential Mechanism in Hokkaido, Japan

Abstract Excerpt:
Chum salmon stock in Hokkaido has been declining since its peak in 2004. In 2017, its stock level reached the lowest level over the past 30 years. In addition, we observed that the stock levels were lower than what we predicted using the sibling regression method. In such a situation, both improving hatchery programs and enhancing the accuracy of the pre-season forecast are essential to managing the chum salmon stock in Hokkaido. We explored factors affecting the variability in-stock level and precision of the pre-season forecast.