Before 1980, birders relied on a telephone grapevine to find out about rarities - now, thanks to modern technology, pagers alert thousands within minutes of something unusual being reported.". Fancy taking part in a shark hunt this month? To get involved with sharks, you might think you need to have scuba-diving skills and to travel towards the tropics. But Britain has its own - admittedly fairly modest - sharks in the form of dogfish, skates and rays. And to find out where they are and what they're doing, you don't even need to enter the water.

Instead, Britain's biggest-ever shark hunt is harnessing our age-old passion for beachcombing. Simply by wandering up and down the strand and poking about in the weeds with a stick, you can contribute more to shark knowledge than any amount of time eyeballing a great white from a cage. It's called the Great Eggcase Hunt. Unlike tropical sharks, which give birth to live young, British dogfish and rays lay eggs. These are very distinctive, being shaped roughly like a parcel of ravioli with horns on the four corners They are known as mermaid's purses. The dogfish purse has long twirling tendrils that anchor the egg to seaweed.The shape of the horns helps to identify the fish that laid them. Skate eggs, which can be as big as an A4 bag, have short, stumpy horns like a bull.

The cuckoo ray has beautiful long horns, which look like the handles of a barrow from the side. By far the most common one, with medium-sized horns, belongs to the thornback ray, Britain's shy, retiring and completely harmless version of the manta ray.Once the baby fish has chewed its way out, the empty case floats to the surface and sooner or later it is cast ashore by the tide. Once on land, the sun dries the case to a blackened, feather-light crisp, which can be blown along by the wind. The best places to find them are beaches backed by an obstacle, such as a cliff or bank of dunes. If soaked in a bucket overnight the cases regain their olive-green colour and pasta-like consistency.The Great Eggcase Hunt is being organised by the Shark Trust, which looks after the interests of sharks and their relatives in Britain and across the world.Ali Hood, a marine biologist who acts as the trust's conservation director, has co-ordinated eggcase hunts on about 600 beaches from Cornwall to Shetland."We have family groups who regularly patrol beaches at home or on holiday, as well as schools and marine centres around the country," Hood says Children are particularly good at spotting them Once you "get your eye in", you tend to find more and more. Some spectacular hauls of mermaid's purses have turned up, especially after a storm.One of the most exciting was a cache of huge brown eggcases, as though a sinking ship had disgorged a cargo of big brown envelopes.

They were found by a party of schoolchildren in Orkney who were taking part in the Hunt as part of an outward-bound project.The extraordinary objects were laid by the so-called common skate - now, unfortunately, very uncommon. "The skate has been lost from 90 per cent of its range," Hood says "Frankly, we've eaten them all. This is a magnificent animal, which grows to three metres long and weighs up to 300lb. Large numbers of eggcases almost certainly point to a nursery near by. If so, this is a completely new and exciting discovery."Such spectacular finds are exceptional, but even the odd eggcase of a relatively common fish like the thornback ray helps to refine what is known about it. "We don't know how far the cases can float," Hood says, "but by talking to fishermen we can tie up finds with local catches."Hood emphasises that even if you fail to find a single case, it's still worth reporting that fact. It is as important to know where British sharks don't occur as where they do."You don't have to go scuba diving to get involved with sharks," she says.

"The Eggcase Hunt allows anybody to go to the beach and walk into a conservation expedition." This is where beachcombing turns into serious biology. The Great Eggcase Hunt is one of many events in the annual Marine Week, which is organised by the Wildlife Trusts and is running to 14 August. Other activities around the country include watching for dolphins and the exciting basking shark, which appears along the coast in late summer to suck up the plankton into its vast gaping jaws. County wildlife trusts have also organised rockpool rambles, strandline walks and even "snorkelling safaris".To take part in the Great Eggcase Hunt, contact the Shark Trust at enquiries sharktrust .for a free eggcase identification chart and records form. Also, you can visit the site at /eggcase. For details of other Marine Week events, see All washed upDRIFTWOODWood that has been in the sea for a long time is usually riddled with worm holes.