Shifting reproductive success in a shoal of Atlantic Cod, Gadus morhua L.
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Individual and temporal variability in the spawning behaviour of Atlantic Cod (Gadus morhua L.) was examined by studying wild and reared individuals from the same putative population in a common spawning arena. The number of eggs fertilized per male was best explained by the number of aggressive interactions initiated by each male. A strong skew in male reproductive success and a temporal shift in male fertilization success were also observed. The latter co-occurred with an apparent similar temporal shift in the reproductive behaviour of the individual males. We hypothesize that energetic costs associated with reproduction, potentially mediated by sperm depletion in dominant individuals, may be responsible for temporal shifts in mating behaviour and reproductive success of male Atlantic Cod. We suggest that this hypothesis merits further study.
KeywordsMating system Aggression Fertilization success Dominance Spawning behaviour
We thank J. Eddington, P. Avendaño and C. Smith for help with the technical labour, analyses of results and input to the experimental set-up. Thanks to T. Nilsen for statistical advice. J. Titelman kindly provided feedback on the manuscript. The research conducted in this study was approved by the Dalhousie University Animal Care Committee and complied with the guidelines of the Canadian Council for Animal Research. The study was sponsored by the Norwegian Research Council-project (172649/S40 entitled, “Interactions between wild and farmed cod; non-lethal impacts of escapees on wild populations)”, and by a Natural Sciences and Engineering Research Council (Canada) Discovery Grant to JAH.
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