Crying blue murder

This is amazing, this river crayfish should be shabby brown but is kingfisher blue. It is beautiful. I never thought I'd say that about Austropotamobius pallipes, the country's only native crayfish species, the White-claw. Blue crayfish are a rare genetic phenomenon, akin to an albino bird or animal.

Blue boy, known as Reggie, is in a tank with its drab brown female mate (Heidi) at Malham Tarn Field Centre, once the remote moortop home of Walter Morrison, a wealthy Victorian who was MP for Skipton and ate crayfish regularly. It is leased from the National Trust by the Field Studies Council and since 1947 it has held outdoor courses for all age groups. It has some 4,000 students a year.

Reggie and Heidi are having babies. The parents arrived last May in a trial from a major education project in Ribblesdale. The female was carrying eggs and these hatched with a 50 per cent survival rate – better than achieved in open streams. The 20 or so youngsters, the size of an earwig, are in a separate tank, safe from the two adults, which may eat them. Now Heidi has conceived with Reggie in the small tank at Malham. This is exciting news for crayfish watchers. It's a bit like trying to breed giant pandas in captivity.

The crayfish are fed with net-loads of stream bottom dredgings, rich in their natural food. This is how the brown trout arrived as a tiny thing. Now it is the size of a decent goldfish and shares the tank with the two adult crayfish.

Robin Sutton, assistant head of the centre is delighted with the response of the students. The younger ones from cities, many of whom have never seen a stream, let alone a crayfish, are immensely interested, says Robin. "They may have watched them on the telly but it's an abstract idea until they see them. Then they almost want to get their heads under water with the crayfish."

This high moors idyll is a spin-off from the country's major crayfish revival programme, which was started in 2000 by a farmer and Environment Agency fisheries officer called Neil Handy. He became worried about the devastation being caused by a water-borne disease, aka plague, and the predation of the American Signal crayfish.

This aggressor is larger, stronger, hungrier and immune to the plague which it spreads. Its activities weaken river banks. It eats anything it can tackle, including small game fish, the eggs of salmon and trout.

It is also the one you'll eat in your deli sandwich, bred for the table in fish farms. It has proliferated in the wild since escaping sometime in the 1970s.

It is as hard to cull as the grey squirrel, yet almost invisible to the public. Neil, who lives near Settle, on the River Ribble, sounded a warning many years ago. If left unmolested, the Signal crayfish could not only wipe out the native White-claw but wreak havoc with the valuable salmon rivers in Scotland. He says this could happen in 10 or 15 years.

In 2003, the Yorkshire Post reported on his plan to breed the crustacean in tanks. It was early days but the tentative signs were promising. We went back in 2005 and he was a little further on. There were young.

They should have been released soon but there have been setbacks. There is no point reintroducing crayfish to wild water until all the Signal crayfish have gone from a river and the plague has burnt itself out.

This will only happen if there are no crayfish to sustain it. You could call it a vicious circle, with claws on it. The Signal can be poisoned using plant-based liquid but that needs to be kept out of public water supplies, and one section in the Ribble network seeps into a village water supply several miles away.

Poison and eradication are emotive issues. So at the moment the work goes on. Neil is looking after White-claws taken for safe keeping from Porter Brook, in Sheffield. He has a second large breeding tank near his home, with the land donated by the farming family and the support of the Manchester Angling Club, which has the fishing rights.

Everyone has a desire to see Neil and his colleagues succeed. His audience includes pupils at a local primary school and at Swallow Hill in Leeds, where one of the anglers is a teacher.

The actual costs, other than Neil's time, are low. At the start there was an English Nature grant of 1,000 for his first breeding tank. More recently, the Environment Agency has given 10,000 towards the second set of breed tanks. Compared to, say, an artist in residence grant, it

is pocket money. The plan is to get a healthy release stock of up to 1,000 White-claws. First, the rivers and streams need to be ready and clean and clear of the Signal species.

"It's an alien species," says Neil, who personally thinks the answer is a determined eradication programme.

The proliferation is evident from the following example. He was asked to provide some Signal crayfish for a research at Lowestoft on how crayfish of all species affected trout and salmon spawning. He handed over a shoal of his captive White-claws and then put a trap in a local stream to get some Signals. The stream was shallow and just a few feet wide. Overnight he got 256 Signals.

He sent off the required batch and boiled the remaining 110 Signals for a Thai green curry meal for eight. The actual crayfish meat content was skimpy. He reports with dry humour: "It took two hours of cracking and de-tailing to get less than one pound of meat."

It is illegal to handle, remove or introduce a crayfish to waterways. Neil is one of the few people with a licence to do this. Malham Tarn and the estate is part of a Site of Special Scientific Interest and access is confined to the Pennine Way footpath.

What next? The research continues, looking at the best captive breeding science. The Malham Tarn eggs will hatch this summer. In time the small population in the tarn may be supplemented with released White-claws where they can proliferate in comparative safety.

Singing the blues

The White-clawed crayfish was once a common feature of many of England's cleanest rivers and streams, and especially abundant in limestone areas of the Yorkshire Dales. This freshwater relative of the lobster can live more than 10 years, grow up to 15cm long, and, until recently, they were an important indicator of the health of some of our finest rivers.

The British Isles supports the greatest remaining concentration of this critically threatened species in Europe. At current rates of decline, the species is predicted to face near extinction within the next 25 years.

The Ribblesdale project team, led by Neil Handy and crayfish specialist Paul Bradley, first succeeded in keeping adult animals in good health. Then in August 2004, a batch of juvenile crayfish were introduced to a tailor-made facility, set into the hillside overlooking the River Ribble.

Of the 102 tiny youngsters introduced, 96 survived the first winter, 64 the second winter, and 59 survived the third winter. In the wild, only a small fraction of juvenile crayfish are likely to reach breeding age.

By April 2008, 53 per cent of the original stock had survived the fourth winter making it the most successful captive breeding of White-clawed crayfish in the British Isles.