Behaviour and thermal experience of adult sockeye salmon migrating through stratified lakes near spawning grounds: the roles of reproductive and energetic states

Abstract

Roscoe DW, Hinch SG, Cooke SJ, Patterson DA. Behaviour and thermal experience of adult sockeye salmon migrating through stratified lakes near spawning grounds: the roles of reproductive and energetic states. Ecology of Freshwater Fish 2010: 19: 51–62. © 2009 John Wiley & Sons A/S Abstract – Little is known about physiological factors underlying thermal behaviour in Pacific salmon ( Oncorhynchus spp.). We implanted acoustic transmitters and temperature loggers into migrating adult sockeye salmon ( Oncorhynchus nerka ) and nonlethally assessed their reproductive hormone levels and energetic states immediately prior to their passing through natal lakes en route to spawning grounds. We tested the hypothesis that energetic and reproductive status influence thermoregulatory and other in‐lake behaviours. More reproductively advanced females with lower levels of energy transited through cooler temperatures compared to less mature females with high levels of energy, possibly to reduce metabolic energy expenditure and delay final maturation. Transit temperatures of males were not related to physiological variables. Salmon travelled on average 13.6 km·day −1 through two lakes, and often circled or held for more than 1 day before moving upstream, but these behaviours were generally not related to physiological variables.