Influence of sex, migration distance, and latitude on life history expression in steelhead and rainbow trout (Oncorhynchus mykiss)

• Published in: Canadian journal of fisheries and aquatic sciences Vol. 71; no. 1; pp. 70 - 80
• Main Authors: OHMS, Haley A, SLOAT, Matthew R, REEVES, Gordon H, JORDAN, Chris E, DUNHAM, Jason B
• Format: Journal Article
• Language: English
• Published: Ottawa, ON NRC Research Press 2014; National Research Council of Canada; Canadian Science Publishing NRC Research Press
• Subjects: Animal, plant and microbial ecology; Applied ecology; Behavior; Biological and medical sciences; Biological productivity; Distribution; Environmental conditions; Exploitation and management of natural biological resources (hunting, fishing and exploited populations survey, etc.); Females; Fish migration; Fish populations; Fishes; Freshwater; Freshwater ecology; Fundamental and applied biological sciences. Psychology; Genotype & phenotype; Growth; Life history; Migration; Migratory species; Oncorhynchus mykiss; Physiological aspects; Rainbow trout; Salmon; Sex ratio; Simulation; Trout; North America; USA; Vertebrata; Life history; Pisces; Migration; Sex; Environmental factor; Latitude; Oncorhynchus mykiss; Distance
• ISSN: 0706-652X; 1205-7533
• DOI: 10.1139/cjfas-2013-0274

In partially migratory species, such as Oncorhynchus mykiss, the emergence of life history phenotypes is often attributed to fitness trade-offs associated with growth and survival. Fitness trade-offs can be linked to reproductive tactics that vary between the sexes, as well as the influence of environmental conditions. We found that O. mykiss outmigrants are more likely to be female in nine populations throughout western North America (grand mean 65% female), in support of the hypothesis that anadromy is more likely to benefit females. This bias was not related to migration distance or freshwater productivity, as indicated by latitude. Within one O. mykiss population we also measured the resident sex ratio and did not observe a male bias, despite a high female bias among outmigrants in that system. We provide a simulation to demonstrate the relationship between sex ratios and the proportion of anadromy and show how sex ratios could be a valuable tool for predicting the prevalence of life history types in a population.