Archival tagging of school shark, Galeorhinus galeus, in Australia: Initial results

Archival tags were used to study the movement and depth behaviour of school sharks, Galeorhinus galeus, in southern australia. Thirty fish were tagged in late 1997, and to date there have been nine recaptures (30% recapture r ate). Periods at liberty varied from 8 days to 18 months. The sharks spent about 80% of their time on the continental shelf, and appeared to swim clos e to the bottom during the day. At night they often ascended for periods of up to several hours, except at times around the full moon. When in deep wa ter, the sharks typically descended at dawn to depths of up to 600 m, befor e ascending at dusk. It was not possible to use the light data from the tag s to estimate position when the sharks were in deep water, because they wer e often at depths beyond the sensitivity of the tag. In shallower water, lo ngitude was estimated from the light data but latitude was estimated from t he maximum daily depth, assuming the fish were on the bottom. The timing of the dives in deepwater appeared sufficiently regular to offer the prospect of using it to estimate longitude. We propose future research using archiv al tags on this species should address questions about female reproductive migrations, pelagic behaviour and vertical movements.