Positive feedback fishery: Population consequences of ‘crab-tiling’ on the green crab Carcinus maenas |
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| Institution: | 1. Faculty of Political and Social Sciences, Av Angel Echevarry s/n, 15782 Santiago de Compostela, Spain;2. Campus Do? Mar, International Campus of Excellence, Spain;3. Consellería do Mar, Xunta de Galicia, Xefatura Territorial de A Coruña, Spain;4. Faculty of Economics and Business Administration, Av Burgo das Nacións s/n, 15782 Santiago de Compostela, Spain;5. Departamento de Ecoloxía e Bioloxía Animal, Facultade de Ciencias do Mar, Campus As Lagoas-Marosende s/n andEstación de Ciencias Mariñas Illa de Toralla (ECIMAT) s/n, Universidade de Vigo 36200 Vigo, Spain;1. College of Transportation and Civil Engineering, Fujian Agriculture and Forestry University, 17 Shangxiadian Road, Cangshan District, Fuzhou 350002, PR China;2. Department of Civil Engineering, Fuzhou University, 2 Xueyuan Road, University District, Fuzhou 350116, PR China;3. Department of Civil Engineering, Ryerson University, 350 Victoria Street, Toronto M5B 2K3, Ontario, Canada;1. Department of Animal Ecology, German Federal Institute of Hydrology – BfG, Am Mainzer Tor 1, 56068 Koblenz, Germany;2. Institute for Integrated Natural Sciences, University Koblenz – Landau, Universitätsstrasse 1, 56070 Koblenz, Germany;3. Bioconsult Schuchardt & Scholle GbR, Reeder-Bischoff-Straße 54, 28757 Bremen, Germany;4. Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany;1. Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK;2. Pathology and Molecular Systematics Team, Centre for Environment, Fisheries and Aquaculture Science (Cefas), Weymouth Laboratory, Weymouth, Dorset DT4 8UB, UK;3. Department of Biomedical Sciences, University of Prince Edward Island, Charlottetown, Prince Edward Island C1A 4P3, Canada;4. European Union Reference Laboratory for Crustacean Diseases, Centre for Environment, Fisheries and Aquaculture Science (Cefas), Weymouth Laboratory, Weymouth, Dorset DT4 8UB, UK;5. Department of Life Sciences, Natural History Museum London, Cromwell Road, London SW7 5BD, UK;6. Department of Animal Science and Aquaculture, Dalhousie University Faculty of Agriculture, 58 River Road, Truro, Nova Scotia B2N 5E3, Canada;7. Epidemiology and Risk Team, Centre for Environment, Fisheries and Aquaculture Science (Cefas), Weymouth Laboratory, Weymouth, Dorset DT4 8UB, UK;1. Department of Communication and Journalism, 438 Dunn Hall, University of Maine, Orono, ME 04469, USA;2. Downeast Institute, USA;3. Department of Communication and Journalism, University of Maine, USA;4. School of Marine Sciences, University of Maine, USA |
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| Abstract: | Collection of marine invertebrates for use as fishing bait is a substantial activity in many parts of the world, often with unknown ecological consequences. As new fisheries develop, it is critical for environmental managers to have high quality ecological information regarding the potential impacts, in order to develop sound management strategies. Crab-tiling is a largely unregulated and un-researched fishery, which operates commercially in the south-west UK. The target species is the green crab Carcinus maenas. Those crabs which are pre-ecdysis and have a carapace width greater than 40 mm are collected to be sold to recreational anglers as bait. Collection involves laying artificial structures on intertidal sandflats and mudflats in estuaries. Crabs use these structures as refugia and are collected during low tide. However, the effect that this fishery has on populations of C. maenas is not known. The impact of crab-tiling on C. maenas population structure was determined by sampling crabs from tiled estuaries and non-tiled estuaries using baited drop-nets. A spatially and temporarily replicated, balanced design was used to compare crab abundance, sizes and sex ratios between estuaries. Typically, fisheries are associated with a reduction in the abundance of the target species. Crab-tiling, however, significantly increased C. maenas abundance. This was thought to be a result of the extra habitat in tiled estuaries, which probably provides protection from natural predators, such as birds and fish. Although crabs were more abundant in tiled estuaries than non-tiled estuaries, the overall percentage of reproductively active crabs in non-tiled estuaries was greater than in tiled estuaries. As with most exploited fisheries stocks, crabs in exploited (tiled) estuaries tended to be smaller, with a modal carapace width of 20–29 mm rather than 30–39 mm in non-tiled estuaries. The sex ratio of crabs however; was not significantly different between tiled and non-tiled estuaries. These results illustrate the potential to manage fished populations using habitat provision to mitigate the effects of fishing pressure. |
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