MEPS 496:135-144 (2014)  -  DOI: https://doi.org/10.3354/meps10524

Theme Section: Tracking fitness in marine vertebrates

Does cortisol manipulation influence outmigration behaviour, survival and growth of sea trout? A field test of carryover effects in wild fish

Jonathan D. Midwood1,*, Martin Hage Larsen2, Mikkel Boel2, Niels Jepsen2, Kim Aarestrup2, Steven J. Cooke1

1Fish Ecology and Conservation Physiology Laboratory, Department of Biology and Institute of Environmental Science, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6, Canada
2National Institute of Aquatic Resources, Freshwater Fisheries, Technical University of Denmark, Vejlsøvej 39,
8600 Silkeborg, Denmark
*Corresponding author:

ABSTRACT: For anadromous brown trout Salmo trutta, the transition from life in freshwater to the marine environment is an inherently challenging and dangerous period characterized by high levels of mortality. As such, smoltification is a relevant life-history phase to examine how physiological state, in particular glucocorticoids, influences fitness-oriented endpoints such as migration timing and survival. We experimentally assessed the effect of cortisol by combining passive integrated transponder (PIT) telemetry with a physiologically relevant exogenous cortisol manipulation (i.e. intracoelomic injection) in juvenile sea trout in the Gudsø Stream, Denmark. Individual survival, migration behaviour (timing and speed), and growth were assessed for 4 treatment categories: control (CO), sham (SH), and low- (LW; 25 mg kg-1) and high-dose (HI; 100 mg kg-1) cortisol. There was no difference in the timing of migration among treatments, but trout in the HI treatment had lower survival rates to the lower station (41.6%) when compared to the CO (53.9%) and SH (52.3%) groups. After migration, the system was electroshocked again to contrast growth of trout that remained in the system. HI, LW and SH individuals recaptured in the stream had lower growth rates for length than the CO treatments; HI and LW also had significantly lower growth rates for mass than CO trout. Future monitoring of this population may demonstrate the long-term repercussions of chronic stress as trout return from the ocean. This study  provides contributions to our understanding of the relationship between organismal condition and fitness while elucidating the potential for carryover effects, i.e. lasting effects that influence future success.


KEY WORDS: Allostasis · Carryover effects · Migration · Stress


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Cite this article as: Midwood JD, Larsen MH, Boel M, Jepsen N, Aarestrup K, Cooke SJ (2014) Does cortisol manipulation influence outmigration behaviour, survival and growth of sea trout? A field test of carryover effects in wild fish. Mar Ecol Prog Ser 496:135-144. https://doi.org/10.3354/meps10524

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