Scallops 'too many to count' in fishing ban zone
April 27 2011 Lewis Smith
Leigh Howarth and Howard Wood survey Lamlash Bay seabed
Scallop numbers in Scotland’s first marine reserve to ban fishing are more than ten times higher than in the surrounding waters, a survey has found.
Just two years after the no take zone was created the number of juvenile scallops is dramatically better than in rest of the Firth of Clyde.
The Clyde was once one of Britain’s richest fisheries but has been devastated by overfishing which has stripped it of its fish and by bottom trawling which has ripped up the seabed, killing plants and animals living on it.
A marine reserve was created in Lamlash Bay, off the Isle of Arran, in 2008 and the first detailed survey since it was established suggests the fishing ban, especially the bar on bottom trawling, is bringing about dramatic and surprisingly rapid improvements to the marine environment.
Initial findings from the survey of the no take zone, which covers one square mile, show not just that juvenile scallops are more abundant but that the adults are bigger, older and have better breeding potential.
Moreover, patches of maerl and seaweed growth, which provide important habitat for commercial species of juvenile fish such as cod, have been found in significant quantities.
The presence of seaweeds is especially important for the scallops, researchers have found, as they seem to provide idea locations for the juvenile shellfish to develop.
Researchers were unable to be categorical that the contrast between the health of sea life inside the reserve and surrounding areas is attributable to the fishing ban because there is a lack of data from previous years. However, the findings are regarded as strongly suggesting the ban is working.
Howard Wood, director of COAST, spent 15 years campaigning for the no take zone and was delighted that the seabed appears to be making a dramatic recovery so soon after fishing was banned.
He was disappointed, though not surprised, that the Scottish Government remains unlikely to extend no take zones to other areas to protect scallops and other creatures.
"Every bit of evidence you see, the scientific evidence, is ignored by the Scottish Government," he said. "They back the big guys. The small and much more sustainable fishermen get very little backing at all."
Mr Wood pointed out that the recovery within Lamlash Bay covers "significant patches" rather than the whole area, as yet, but he was relieved the sea bed "is beginning to support life" again.
A spokesman for the Scottish Government described the findings as "encouraging" and said proposals for changes to the way the scallop fishing is managed in Scotland are being considered.
Equipment used by scallop dredgers drags along and tears up the seabed, destroying the habitats that many creatures rely on. Underwater surveys of the Lamlash Bay no take zone were carried out last year in partnership with researchers from the University of York and are reported in the journal Marine Biology.
Divers conducted 40 dives to assess the number of scallops and other organisms inside and outside the reserve.
The study assessed numbers of the great scallop, Pecten maximus, and those of the queen scallop, Aequipecten opercularis. Great scallops are the more important catch, being worth £38.8 million in 2007, making them Britain's fifth most valuable catch, compared to £2.2 million for queen scallops.
More adult scallops were found inside the zone than outside it, though the difference was too small to be statistically significant. They were, however, bigger and older with the great scallops being 1.2 times larger and 1.3 times older. Queen scallops were 1.1 times bigger – a figure not considered significant by scientists – but were 1.5 times older on average.
The size difference was considered particularly important because were they to be caught those great scallops in the no take zone had up to 44 per cent more of the meat demanded by the seafood industry.
With the number of young that the adult shellfish are able to produce being directly related to their size and age, it was found that great scallops inside the marine reserve were likely to have considerably more offspring.
Dr Bryce Beukers-Stewart, of the University of York, described the findings as a "win win scenario" and said: "Marine reserves like this can benefit both fishermen and conservationists." The number of juveniles in the entire zone had to be estimated on the basis of sample counts. There were, he said, "too many to count" individually.
Fishing restrictions in other scallop fisheries, such as off the Isle of Man, have previously demonstrated that no take policies allow marine ecosystems to recover from overfishing but the speed of improvement in Lamlash Bay came as a surprise.
The data also provides a baseline against which further surveys can be compared. Leigh Howarth, an MSc student involved in the research, said: "Marine ecosystems can continue to recover for decades when protected inside reserves, the reason this study is so exciting is because this is just the beginning."
* In a separate study, four in every five langoustine - also known as nephrops and served as scampi - caught in the Clyde estuary contain strands of plastic, many of them from ropes and nets used by trawlers. The plastic forms balls in their stomachs, damaging their ability to eat, and raises the potential of toxins being eaten by people. The study was by researchers from the University of London and the University of Aberdeen.
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