Behaviour of growth hormone transgenic coho salmon Oncorhynchus kisutch in marine mesocosms assessed by acoustic tag telemetry

Underwater acoustic tag telemetry was used to assess behavioural differences between juvenile wild‐type (i.e. non‐transgenic, NT) and growth hormone (GH) transgenic (T) coho salmon Oncorhynchus kisutch in a contained simulated ocean environment. T O. kisutch were found across days to maintain higher baseline swimming speeds than NT O. kisutch and differences in response to feeding were detected between T and NT genotypes. This is the first study to assess behaviour of GH transgenic salmonids in a marine environment and has relevance for assessing whether behavioural effects of GH overexpression seen in freshwater environments can be extrapolated to oceanic phases of the life cycle.