Fishermen off the coast of west Wales are catching and tagging sharks as part of a major research project.
This blue shark was caught 25 miles off Pembrokeshire
Conservationists are trying to find out more about the sharks that populate UK waters by monitoring their movements and behaviour.
The scheme has been organised by the World Wildlife Fund (WWF).
Among the most common sharks off the Pembrokeshire coast are blue sharks, which are grey-blue and have skin covered in tooth-like scales.
Adding tags mean that, if the sharks are recaptured anywhere in the world, details the tag can be forwarded to conservationists in the UK.
Simon Walmsley from the WWF said the details could be extremely useful, especially as sharks could travel great distances.
"If we can find out where they are actually breeding or where their food sources are, then we can at least advise on how we can protect the species from various things that happen at sea like commercial fisheries," he said.
Steve Hambidge, one of the skippers involved in the scheme, said the aim was to keep the process brief to avoid unnecessary stress.
"What we do is do the job as quickly as possible, and generally speaking they won't be on deck for more than a couple of minutes," he said.
The anglers tag the sharks before releasing them
"We get them in, get them tagged, measure, photograph and slide them back in the water."
Sally Bailey from the WWF said the organisation was trying to protect future populations of blue sharks, which are rarely spotted in the wild.
"We have this vast array of wildlife but just because we don't see it, we don't always appreciate it is there, so it is really important that we actually build up information about these species.
"Unfortunately, quite often we only find out about them when they have been washed up on the shore."