Long-term Changes in Length at Maturity of Pacific Salmon in Auke Creek Alaska

Although decreasing length at maturity has been observed in some Alaska salmon populations, the generality of this trend is poorly understood. This study was undertaken to determine whether this pattern holds for multiple species of salmon from a small watershed in Southeast Alaska (Auke Creek), and, if so, what abiotic and biotic factors are contributing to this phenomenon. We analyzed up to 32 years of data (early 1980s - 2012) for coho salmon (Oncorhynchus kisutch), sockeye salmon (O. nerka), and pink salmon (O. gorbuscha). We observed statistically significant decreases in mean length at maturity for coho salmon adults, as well as increases in mean length of saltwater age-2 sockeye salmon. Non-significant trends in mean length were observed in coho salmon jacks, pink salmon, and saltwater age-3 sockeye salmon. Abiotic and biotic variables that explained interannual variation in length include a combination of climate and resource availability effects. These observed changes should be considered in future management decisions to ensure sustainable harvest for Southeast Alaska’s sport, commercial, and subsistence fisheries.