Foraging is a behavioural process and, therefore, individual behaviour and diet should co- vary. However, few comparisons of individual behaviour type and diet exist in the wild. We tested whether behaviour type, diet and body size covary in a population of Atlantic cod, Gadus morhua. Working in a no-take marine reserve, we could collect data on natural behavioural variation and diet choice with minimal anthropogenic disturbance. We measured behaviour us- ing acoustic telemetry and diet with δ13C and δ15N stable isotopes. We further investigated whether behaviour and diet could have survival costs. We found more active cod consumed resources with a higher contribution from pelagic primary production and cod with shorter diel vertical migration (dvm) distances fed at higher trophic levels. Cod δ13C and δ15N scaled posi- tively with body size and larger cod had shorter dvms suggesting dvm may act as a behavioural link between diet and body size in coastal cod populations. Neither behaviour nor diet pre- dicted survival, indicating phenotypic diversity is maintained without survival costs for cod in a protected ecosystem. Our findings emphasize that, along with body size, individual behavior indeed plays a role in trophic interactions, and the effect of individual behavioural composition on community dynamics requires research attention

6th International Conference on Fish Telemetry, Sète (France), 11-16 June 2023

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