By Heather Chinn
Scotland's first and only fully protected marine reserve shows promise for European lobster conservation but there is still room for improvement, according to scientists.
Adult lobsters from the’No Take Zone’ in Lamlash Bay off the Isle of Arran in the Firth of Clyde were found to have more than doubled in number, got bigger and to be twice as likely to carry fertilised eggs as lobsters from outside the conservation area.
Tagging studies also showed the crustaceans are spreading out from the reserve, which is roughly the size of a square mile and where all fishing activity was banned by the Scottish Parliament in September 2008 in a bid to reverse the steep decline in fish and shellfish stocks caused by more than a century of intensive fishing.
With the Scottish lobster fishery generating around £10.6 million in 2013 the findings of the four-year research project, begun in 2012, are encouraging for the local Community of Arran Seabed Trust (COAST), which had lobbied for the no take zone for over a decade.
But the scientists from the University of York, who also surveyed Lamlash Bay’s brown crab and velvet swimming crab populations, warn the protection zone cannot be considered an unqualified success.
Numbers of brown crabs, a species even more valuable to the Scottish fisheries and estimated to have generated £13.8 million in 2013, and of velvet swimming crabs - worth £4 million to the Scottish fisheries in the same year - appeared to decline inside the reserve as the population of adult lobsters rose.
The numbers of juvenile lobsters also seemed to drop, suggesting competition for food or predation by the adult lobsters is reducing the population of the two crab species and the young lobsters.
And, while the population of adult lobsters more than doubled within the reserve over the years of the study, the gains were not as high as in other marine protection zones.
Adult lobster numbers also showed an annual decline both outside and inside the reserve in the last two years of the survey.
Researchers suspect intensified fishing immediately outside the area of the ‘No Take Zone’ and a lack of suitable habitats for lobsters in parts of Lamlash Bay are limiting the growth of the adult lobster population.
The team believes its findings, published in the ICES Journal of Marine Science, suggest small marine reserves the size of Lamlash Bay are unlikely to be a solution to regenerating fish and shellfish stocks in isolation. Other conservation measures will also be needed.
Leigh Howarth, who led the study, and is now with Bangor University’s School of Ocean Sciences, said: “Marine reserves are only one part in creating sustainable fisheries. It is widely agreed that a combination of managing fishing effort, fishing gears, and establishing protected areas, all of which have received mutual consent from managers, fishers, and other stakeholders, is by far the most effective way to restore stocks and marine ecosystems.”
And Bryce Beukers-Stewart, a lecturer in the University of York’s environment department and supervisor of the study, added: “Our findings provide evidence that temperate marine reserves can deliver fisheries and conservation benefits, but they also highlight the importance of investigating multi-species interactions, as the recovery of some species can have knock-on effects on others.”
Picture credit: Howard Wood