Tracking fish with electronic tags

The distributions of many species of fish show pronounced seasonal changes as a result of migration1. We are using long-term electronic tagging to study the migratory behaviour of fish in the North Sea. Using simple measurements of depth and temperature, we have found that we can reconstruct the tracks of plaice (Pleuronectesplatessa) migrating between the southern North Sea and their spawning areas in the eastern English Channel or northeast coast of England. In this way we show that fish can visit more than one spawning area within a single spawning season and that rates of movement are often ten times faster than those deduced from conventional mark-recapture experiments.