The dispersal patterns and behaviour of North Sea cod (Gadus morhua) studied using electronic data storage tags

The migratory behaviour of adult cod was studied using electronic data storage tags (DSTs). Fifty-eight cod were externally tagged with LOTEK LTD-100 DSTs and released off Lowestoft in March and April 1999. Twenty-two tags were returned by March 2000. Individuals demonstrated significant shifts in behaviour patterns that were associated with migration and residence on feeding grounds. During migration, individuals were very active and utilised a large vertical range. In contrast, individuals demonstrated low activity and a much reduced vertical range whilst on summer feeding grounds. Use of the Tidal Location Method showed that individuals dispersed to feeding grounds in the central and southern North Sea. Our results demonstrate that individual-based studies of fish behaviour can provide information relevant to fisheries management.