tagged with an electronic data storage tag on 6 october 1999 in the thames estuary (uk), a thornback ray, raja clavata, was recaptured after 504 days at liberty, 276 km north-west of release. the tag recorded 423 days of data. the migration was reconstructed using the tidal location method, and illustrates seasonal migration out of the thames estuary to the central southern north sea during autumn and winter, then a return to the thames to spawn during spring. this is the first direct evidence of repeated seasonal migration outside the area commonly thought of as the species home range, an observation with significant implications regarding the applicability of closure management as a conservation measure for this species.