Spatio-temporal dynamics of Atlantic cod (Gadus morhua) in the Irish and Celtic Sea: Latest results from a collaborative tagging programme (as of January 2012)

Using data from mark recovery and electronic tag studies, we investigate the exchange of cod between three adjacent cod management areas; the Irish Sea (ICES Division VIIa), Scottish waters (ICES Division IVa) and in the western English Channel and Celtic Sea (ICES Divisions VIIe-k). We evaluate 2209 archived and current mark recovery data (1960’s – to 2010) to assess the seasonal changes in distribution of cod within ICES Divisions VIa, VIIa and VIIe-g.  In addition, we report on the results of a collaborative electronic data storage tagging (DST) programme of cod in the Irish and Celtic Sea, spanning the years 1999 to 2010.  During this time, 710 DSTs have been deployed on cod between 43cm and 110cm, and 107 of the tags have been returned yielding over 11000 days of data.  We use a tidal geolocation model to determine the daily locations of each cod to reconstruct in detail the migrations of cod tagged with DSTs. The results describe fundamental features of cod spatial ecology in the Irish and Celtic Sea, such as the seasonality of migration and habitat occupation and the potential impact upon sub-stock structure.