Schotland, 21 oktober 2008 – het gaat kennelijk niet goed met de gewone zeehond in de Engelse en Schotse wateren. Lees het artikel in de Scotland Guardian.
>> The Guardian
Marine biologists have warned of significant and serious changes in the seas around Britain after detecting a steep and “frightening” fall in the numbers of common seals around the coast.
Common seals are one of Britain’s largest and most charismatic marine predators and the most likely to be seen by holidaymakers and sailors. But the latest surveys have revealed a dramatic decline in their numbers in Scotland’s waters and along eastern England.
In the worst affected areas, such as the Orkney islands, the numbers of common seals are falling by 10% a year, and have dropped by as much as half in the past six years. Along the Argyll coast, from Oban to the Mull of Kintyre, the numbers fell by a quarter last year.
Ian Boyd, a professor with the sea mammals research unit at St Andrew’s University, said it was as if the entire population had stopped breeding.
The cause was baffling scientists. “We just don’t know,” he said. “Our collective view is that there’s some large-scale process going on in the northern North Sea which is driving down seal numbers. We’re seeing a massive decline. It’s quite a frightening decline because these populations don’t change as quickly as that under normal circumstances.
“This is very abnormal. To give you an idea of the level of abnormality, the rates of decline are equivalent to these populations producing no offspring for five or six years.”
The steep declines mirror other crises in the marine environment. Biologists have reported plummeting sea bird populations, with falls of a third in numbers of puffins on the Farne islands off the Northumberland coast, and the Isle of May at the Firth of Forth, as well as declines in food sources for mammals and birds, such as sand eels. At the same time, warmer-water animals from plankton through to large fish are moving north.
Boyd said it was too early to say whether climate change was directly connected to the collapse of seal populations. He said his unit and other marine biologists were investigating a number of possibilities, including the theory that common seals – also known as harbour seals – were up against stiff competition from the larger, more robust grey seals for increasingly scarce food supplies.
Some studies suggested that killer whales, now hunting in larger numbers around Orkney and Shetland, were killing seals at pupping time.
People could be illegally shooting the seals in fish-farming areas and at inshore fishing grounds. But Boyd said these problems were localised and could not explain the UK-wide declines. The causes were likely to be complex.
The latest findings will be raised at a conference this month in Edinburgh run by the conservation agency Scottish Natural Heritage, which will give conservationists the chance to debate the challenges of climate change, alien species and conflicts between species, including common and grey seals.
All the main environment groups want the Scottish government to use powers under the proposed marine bill for Scotland to legally protect common seals, by abolishing the Seal Conservation Act 1970, which allows salmon farmers and the fishing industry to legally shoot seals that appear to damage their nets. Instead, seals should be a protected species under the Wildlife and Countryside Act, they say.
The Guardian has learned that the latest figures show that last year common seal numbers fell from 4,256 to 3,379 in Orkney, from 1,056 to 800 along the eastern coast of the northern Highlands, from 113 to 102 in the north-east, in Grampian, and from 6,702 to 4,732 on the west coast from Oban to the Mull of Kintyre. There was also a fall, from 445 to 215, in Fife, and by nearly half in the smaller populations around Lothian and Dumfries and Galloway.
In English waters, smaller populations at the nature reserves at Blakeney Point, in Norfolk, and Donna Nook, in Lincolnshire, also fell sharply.
Some areas have shown increases, particularly the Wash, where numbers rose from 1,695 to 2,162 last year. But total numbers across the UK fell by 12% last year at the 13 sites where counts were made over two years – down by 3,120 animals to 23,277, a drop that early figures suggest has continued this year.
Boyd said that, by contrast, there had been “rapid growth” in the nearest population on the continent, in the Wadden Sea, off the Dutch, German and Danish coasts. “We ought to be worried because these animals are at the top of the marine food chain and are in a sense bellwethers of what’s going on in the marine environment,” he said. “Quite apart from the fact that they’re charismatic species, they’re indicators of the level of robustness that there is within the marine environment, and if we’re seeing populations declining rapidly like this, it’s got to ring alarm bells.”
John Baxter, a senior marine biologist with Scottish Natural Heritage, said the agency shared was helping investigate the decline. “These fluctuations are very large, and we’ve no way of knowing whether there’s a natural fluctuation and numbers may recover, or whether there’re more serious underlying causes.”