Co-operative members are being recruited to take part in egg hunts with a difference - they will be looking for shark eggs on beaches.
The Shark Trust's "great eggcase hunt" will see volunteers heading to the coast to search for the eggcases, known as "mermaid's purses", in which the young of many skates and rays and some sharks are laid.
They will use an identification guide to discover which species hatched from the egg and record the location where it was found, as part of conservation efforts to ensure the UK's shark species are adequately protected. Recent estimates suggest almost 100 million sharks are being caught worldwide by commercial fishing fleets, with sharks' fins being used for a soup delicacy in Asia.
Governments this week agreed to boost protection for five species of shark under a global treaty governing trade in endangered species, so the trade in them is regulated to ensure it is sustainable.
Over half the 50 species of sharks, skates and rays found in British waters are classified as threatened or near-threatened with extinction. But little is known about their breeding areas and population sizes, making it hard to ensure sufficient protection for them.
John Atkinson, environment adviser at the Co-operative, said: "By taking part in the great eggcase hunt our members can help to identify areas of the coast where the eggcases of certain species have washed up. This may indicate nearby nursery ground, identification of which could inform future fisheries management plans and assist shark, skate and ray conservation."
The Co-operative is working with its members, pupils in 5,000 schools signed up to the group's "green schools revolution" sustainability education programme and the Shark Trust to get people involved in the egg hunt. It is hosting seven events around the UK in the coming months, which will see an expert from the Shark Trust explaining to hunters what they need to know about eggcases, how to identify them and how to record their finds.
Many species of skates and ray and some sharks reproduce by laying leathery eggcases which remain on the seabed or attached to seaweed for several months while the embryo develops into a miniature version of the adult. Once the young have hatched the eggcases can be picked up in currents and washed up along the shore.
Cat Gordon, conservation officer at the Shark Trust, said: "The great eggcase hunt was established in 2003 and more than 33,000 individual eggcases have since been recorded."
She said linking up with the Co-operative and the green schools revolution would help increase knowledge of the distribution of British egg-laying species of sharks, rays and skates.