Sammendrag
Among the component of climate fluctuations and change, environmental temperature is a key parameter influencing teleost physiology and population dynamics. In Atlantic cod, a species of great ecological and commercial interest in the North Atlantic, earlier results indicate that body size (allometrics) may play a central role in defining how the reproductive performance of an individual is influenced by environmental parameters but also that the spawning stage seems particularly sensitive due to the narrow thermal window. Therefore, the aim of this study was to understand how temperature can impact cod reproductive physiology. To address this question, 200 wild-caught Norwegian coastal cod of different sizes were randomly distributed into twelve tanks (3 replicates per temperature) in recirculated aquaculture system at 3, 6, 9 and 12 °C. From the onset of the reproductive cycle (September) to the end of the spawning season (April), PIT-tagged fish were sampled every month to track growth and condition index, hormones and vitellogenin variations but also oocyte maturation. During the spawning season, eggs were daily collected to determine volume, embryonic stage and egg quality. From early embryogenesis to hatching, developmental success was also studied. To do so, 20 spawns per temperature were incubated. Furthermore, eggs gene expression was investigated. So far, we have found that individuals may spawn in every condition, but that temperature clearly affects gamete quality. Key results will be presented in the context of global change that could be helpful for predictive-type models.
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