Diversity of life history traits, growth, and lipid storage in migratory variants of steelhead and rainbow trout (Oncorhynchus mykiss) in Kamchatka, Russia

Abstract

Partial migration in salmonids provides access to freshwater and marine feeding environments varying in productivity. To test the hypothesis that partial migration drives differences in growth and energy storage with differential consequences for females than males, we assigned Oncorhynchus mykiss sampled on the western Kamchatka Peninsula, Russia, to one of five life history contingents based on scale patterns. Stable isotopes, obtained from a subset of fish, indicated different foraging by fish showing oceanic and coastal anadromous life histories. In younger fish, body size was largest in anadromous fish feeding on the high seas, intermediate for those feeding in coastal environments, and smallest for nonanadromous fish feeding in rivers. Older fish converged on large (oceanic) and small (coastal and freshwater) body sizes. Somatic lipid content, also collected for a subset of fish, averaged 2.5% across all life histories. Percent lipid was highest in females of ocean and males of coastal and freshwater life histories. Taken together, migratory patterns predictably influenced growth but may limit compensatory lipid storage in females, especially for the rare life histories.