Spatial dynamics of Atlantic cod (Gadus morhua) in the North Sea: results from a large-scale electronic tagging programme

No abstracts are to be cited without prior reference to the author.

Electronic tags have revolutionised research into the behaviour of free-ranging marine fish. With the right analytical tools they can provide insights into movements, habitat occupation and environmental preferences. Here, we report on the results of a large-scale electronic tagging programme of Atlantic cod in the North Sea, spanning the years 1999 to 2008. During this time, 1126 tags have been deployed on cod between 37cm and 110cm, and 263 of the tags have been returned yielding over 31,000 days of data. We used a tidal geolocation model to determine the daily locations of each cod, and to ascertain the scale and rate of their movements. We have used this dataset to describe fundamental features of cod ecology, such as the balance between homing and resident behaviour, the location of feeding and spawning grounds (and the migratory pathways between them), and the seasonality of migration and its impact upon sub-stock structure. The results provide a step forward in our understanding of how Atlantic cod exploit and utilise their environment and, as a result, have implications for our expectations of how cod stocks may recover following depletion.