A hump-shaped relationship between migration distance and adult pink salmon morphology suggests interactive effects of migration costs and bear predation

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Sahashi, Genki, Yoshiyama, Taku
• Other Authors: Taylor, Eric
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2016
• Subjects: Oncorhynchus gorbuscha; Pink salmon
• Online Access: http://dx.doi.org/10.1139/cjfas-2015-0176; http://www.nrcresearchpress.com/doi/full-xml/10.1139/cjfas-2015-0176; http://www.nrcresearchpress.com/doi/pdf/10.1139/cjfas-2015-0176

We examined the relationship between environmental factors of a spawning habitat and body shape at maturity in 16 pink salmon (Oncorhynchus gorbuscha) populations. The divergence vector (indicator of body depth and head size development) in both sexes was significantly correlated with distance from the sea and was described by a hump-shaped relationship. An exaggerated body shape was most developed at mid-distance from the sea and less developed both near and far from the sea. The observed frequency of bears decreased significantly with distance from the sea, implying that bear predation on salmon is most intense near the sea. Therefore, our results imply that shape-selective predation by bears affects the shape of pink salmon in rivers where the spawning habitat is near the sea and that migration costs inhibit development of an exaggerated body depth and head size in salmon in rivers where the spawning habitat is far from the sea.