The behavioural diversity of Atlantic cod: insights into variability within and between individuals

Cod (Gadus morhua) are an iconic fish species of cultural, historical and economical significance across the Atlantic and adjacent seas. Among many scholarly investigations, this interest has prompted behavioural research, rendering cod one of the few commercially harvested marine fishes for which behaviour has been studied in a comprehensive manner. In our review of this behavioural work, we examine the variability in cod behaviour across five functional domains: foraging, predation, social interactions, migration and reproduction. Research to date suggests a high level of behavioural sophistication in cod that is underpinned by complex learning strategies and long-term memory. Cod also demonstrate substantial variability in how they respond to different ecological circumstances. Considerable variation is evident both within and between individuals, and in some instances, between populations. There are a number of pathways from which this variation appears to arise, such as asocial and social learning, environmental control of phenotypic plasticity and genetic control, but there are no known examples of behaviours that are purely the result of one of these mechanisms. Behavioural variation is therefore likely to result from a combination of these factors, underscoring the need for a quantitative, multivariate approach to understand behavioural variation in cod.