Sands of time are running out for shellfish

Another Life: You'd wonder why the piping oystercatchers bother with my bit of shore, where virtually the only shellfish on offer between the tides are tiny blue mussels packed tight on rocks pounded by Atlantic breakers.

Perhaps little and often is the reward, but all that hammering for food must be hard on their bills. An oystercatcher's daily intake is 40 per cent of its body weight - more than 80 kilos in a year.

This was never their consumption of oysters, but try saying "cocklecatcher" a few times and you'll get the point. Cockles are the bird's primary food and draw them in great flocks in winter to the muddy bays of the Irish Sea - 150,000 to the west coasts of England, another 10,000 to Ireland's Dundalk Bay alone. On both coastlines they enter an uneasy balance of commerce and ecology.

The tragedy of the Chinese cockle-pickers out in Lancashire's Morecambe Bay came late in a period of extraordinary plunder of the bay's cockle resource - perhaps 1,000 pickers at one time in 2004, where 100 would have been quite sustainable. The consequence, last April, was the first-ever ban on harvesting to give the beds a chance to recover, and the promise of a closed season from May to September (plus health-and-safety leaflets in Polish and Chinese).

The oystercatchers may be suffering, too. It's common, in bad weather, for the birds to switch to inland earthworms for food (urban football pitches are a favourite foraging ground), but, as reported in the Morecambe Visitor last month, the degree to which the local oystercatchers have deserted the cockle beds has become worrying. The RSPB, the local sea fisheries committee and English Nature will have an early meeting.

In Scotland's Solway Firth, cockle stocks were so severely over-fished in the 1990s that harvesting is still banned. In Wales, computer-modelling has been recruited to decide an annual Total Allowable Catch. In Cornwall, where "gangs of pickers riding tractors" have been pillaging the estuaries, the Environment Agency has sought a bye-law to favour traditional hand-harvesters.

Which brings us back across the Irish Sea to Dundalk Bay, right opposite Morecambe, where more than 4,000 hectares of sand and mud-flats support a notable stock of cockles - 143 million of them, or 1,650 tonnes, when Marine Institute scientists did a survey in spring 2004. That was after the oystercatchers and other birds among the bay's 50,000-odd migrant waders had eaten their winter share, estimated at a further 1,500 tonnes.

These figures seem substantial enough, but fishermen recognise a depletion, for Dundalk Bay, too, has had its cockle "gold-rush". In 2001, three vessels dredged almost nine tonnes; by 2003, some 10 dredgers landed 177 tonnes and damaged a great deal more by mechanical discarding of the same small juveniles, scooped up over and over. All this is happening in a bay designated as a Special Area of Conservation and a Special Protection Area for Birds.

The Marine Institute's Stock Book for 2006 has repeated, for a third year or more, its advice to the Minister: "This fishery urgently requires a management initiative which recognizes the inherent restrictions on exploitation imposed by European conservation legislation." And, to deal with the damage to juvenile cockles, "A close season should be put in place by regulation and enforced." Many of the fishermen have voluntarily respected a closed season in the spring months, when essential spat settlement takes place. But others have not, and competition is increasing, even to nudging their suction dredgers tight inshore at the top of the highest spring tides.

The last free-for-all for shellfish on the east coast wrecked a new razor-clam bed of 21sq km discovered at Gormanstown, Co Meath, in 1997. Over the next two years, some 50 boats used custom-built hydraulic dredges to scour the long-lived clams out of the fine sand. By 1999 about two-thirds of them were gone - about 1,000 tonnes, mostly sold to Spain to make paella for the tourists.

When the Gormanstown beds were exhausted, eyes turned to Connemara, where a smaller, but very marketable species of razor clam lives in beds of maerl - the species-rich "coral sand" of the region's inner bays. The beds have already been depleted, and while the mechanics of fluidised dredging has been refined since the early Gormanstown days, it still causes, says the Marine Institute "considerable incidental damage and disturbance" to the seabeds it harrows, and was being used in Connemara bays last month. The new stock book, calling for the umpteenth time for "special and urgent consideration" of the fishery, even urges letting divers making a controlled harvest of the clams (a practice currently illegal). At least they could select their quarry without wrecking the sediment and a "less stressed animal" would be even more marketable.

• In the recent column on ferrets, the wrong mobile phone number was given for Daniel Buckley; it should have been 086-3691982