title: Fitness and behavioral correlates of pre-stress and stress-induced plasma cortisol titers in pink salmon (Oncorhynchus gorbuscha) upon arrival at spawning grounds.
abstract: Semelparous Pacific salmon (Onchorynchus spp.) serve as an excellent model for examining the relationships between life history, behavior and individual variation in glucocorticoid (GC) stress hormone levels because reproductive behaviors are highly variable between individuals and failure to reproduce results in zero fitness. Pink salmon (O. gorbuscha) were intercepted upon arrival at the spawning grounds across three time periods. Pre-stress and stress-induced plasma cortisol concentrations were assessed in relation to behavior, longevity and reproductive success. Results revealed differences between sexes and with arrival time. The study period marked a year of high reproductive success and only nine females (12% of sample) failed to spawn. Female pre-spawn mortalities were characterized by significantly elevated stress-induced cortisol concentrations and decreased longevity as well as pre-stress cortisol above the normal range in pink salmon from the study area. Interestingly, reproductive behaviors were only associated with pre-stress cortisol levels. For females, aggression and mate interaction time were reduced in individuals with elevated pre-stress cortisol concentrations. In males, a similar negative relationship between pre-stress cortisol concentration and mate interaction time was detected. The observed behavioral correlations are likely a factor of social status where dominant individuals, known to have higher reproductive success, are characterized by lower cortisol levels relative to subordinate conspecifics. Findings show both elevated pre-stress and stress-induced cortisol concentrations at arrival to the spawning grounds to be associated with reduced survival.
authors.affiliation: Fish Ecology and Conservation Physiology Laboratory, Biology Department, Carleton University, 1125 Colonel By Drive, Ottawa, ON, Canada K1S 5B6. katrina.vcook@gmail.com
authors.forename: K V
authors.initials: KV
authors.lastname: Cook
authors.forename: S H
authors.initials: SH
authors.lastname: McConnachie
authors.forename: K M
authors.initials: KM
authors.lastname: Gilmour
authors.forename: S G
authors.initials: SG
authors.lastname: Hinch
authors.forename: S J
authors.initials: SJ
authors.lastname: Cooke
mesh_terms: D000374:Aggression / Q000502:physiology; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D004291:Dominance-Subordination; D005260:Female; D005298:Fertility / Q000502:physiology; D056084:Genetic Fitness / Q000502:physiology*; D006854:Hydrocortisone / Q000097:blood*; D008136:Longevity / Q000502:physiology; D008297:Male; D012474:Salmon / Q000502:physiology*; D012726:Sexual Behavior, Animal / Q000502:physiology; D013312:Stress, Physiological / Q000502:physiology
chemical_list: D006854:Hydrocortisone