Used to study the migration and behaviour patterns of tope sharks in the North Sea, the satellite tracker is part of a research project for the German Thunen Institute of Sea Fisheries in Bremerhaven.
It has detached from the shark after a pre-programmed period and is now drifting between Guernsey and Alderney.
Researcher Dr Matthias Schaber, from the institute, said the detached tag had started transmitting on Monday.
‘The tag that is currently floating around the islands was attached to a comparatively small female shark at 132cm – the smallest of all sharks I tagged in this project,’ he said.
‘Unfortunately, it has not been transmitting data in the last 15 hours, which worries me a bit.
‘Of course, in severe weather, the tag may not get a satellite uplink and I figure there has been quite some wind.’
The tags are programmed to detach after 270 days and float to the surface and transmit the recorded data via satellite until the battery expires.
More-detailed data can be collected if a detached tag can be recovered.
Three reports have been received so far from the five sharks tagged in 2019.
‘From the data transmitted so far I cannot yet infer a migration route,’ added Dr Schaber.
‘But based on the previous results of tags that reported, the sharks seem to leave the area around Heligoland in late summer and swim across the North Sea to the British coast or along the Dutch coast to then go into the Channel in the winter months.
‘Two of the three sharks that reported, excluding this tag, seemed to spend some time in waters around the Channel Islands in winter.’
A tag was found washed ashore on a Jersey beach last year and returned, so Dr Schaber is hopeful the same can be done again.
‘It was absolutely great to have one returned,’ he added. ‘It’s like looking for a needle in a haystack, the haystack being the Atlantic Ocean.
‘The drift pattern looked like it was about to probably end up on one of the islands, so I started a Facebook request in relevant groups hoping that somebody probably would find and report the tag and this is what happened. It was really cool how many people helped and with success.’
n If you find the tag, contact Dr Schaber via the information provided on its label or by emailing firstname.lastname@example.org.