16 research outputs found
Recovery of a temperate reef assemblage in a marine protected area following the exclusion of towed demersal fishing.
Marine Protected Areas MPA have been widely used over the last 2 decades to address human impacts on marine habitats within an ecosystem management context. Few studies have quantified recovery of temperate rocky reef communities following the cessation of scallop dredging or demersal trawling. This is critical information for the future management of these habitats to contribute towards conservation and fisheries targets. The Lyme Bay MPA, in south west UK, has excluded towed demersal fishing gear from 206 km(2) of sensitive reef habitat using a Statutory Instrument since July 2008. To assess benthic recovery in this MPA we used a flying video array to survey macro epi-benthos annually from 2008 to 2011. 4 treatments (the New Closure, previously voluntarily Closed Controls and Near or Far Open to fishing Controls) were sampled to test a recovery hypothesis that was defined as 'the New Closure becoming more similar to the Closed Controls and less similar to the Open Controls'. Following the cessation of towed demersal fishing, within three years positive responses were observed for species richness, total abundance, assemblage composition and seven of 13 indicator taxa. Definitive evidence of recovery was noted for species richness and three of the indicator taxa (Pentapora fascialis, Phallusia mammillata and Pecten maximus). While it is hoped that MPAs, which exclude anthropogenic disturbance, will allow functional restoration of goods and services provided by benthic communities, it is an unknown for temperate reef systems. Establishing the likely timescales for restoration is key to future marine management. We demonstrate the early stages of successful recruitment and link these to the potential wider ecosystem benefits including those to commercial fisheries
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Spatio-temporal variations of sea star Asterias spp. distributions between sea scallop Placopecten magellanicus beds on Georges Bank
Presently 80 % of the biomass of sea scallop Placopecten magellanicus on Georges Bank is located within 3 large areas closed to fisheries. Sea stars Asterias spp., primary predators of scallops, are also aggregated within these closed areas. As prey becomes depleted within one scallop bed, sea stars may move to another food source, possibly to another scallop bed. We tested the hypothesis that sea star aggregations moved from one scallop bed to another within the Nantucket Lightship Closed Area (NLCA) on Georges Bank. We video surveyed 204 stations in the NLCA from 1999 to 2006 using a 1.57 km grid-centric systematic sampling design. The center of sea star abundance was calculated by averaging the sea star frequency-weighted latitude and longitude for all stations. Using multivariate analysis of variance and all-pairs comparisons (Hotelling\u27s T2), shifts in the center of sea star abundance were determined by assessing if the locations of the 2 aggregations were different. The sea star center of abundance, standard ellipse and 95% confidence ellipse were superimposed on the scallop density distribution maps to determine the spatial overlap. The distributions of sea star aggregations in the NLCA significantly shifted between consecutive years from 1999 to 2006 and overlapped with areas of high densities of scallops. Shifts in the center of abundance reflect changes in distribution possibly resulting from movement, recruitment and mortality. As sea stars aggregate in these areas presumably due to high abundances of scallops, sea star movement between the scallop beds may increase natural mortality rates of the scallop population on Georges Bank
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Effect of closed areas on populations of sea star Asterias spp. on Georges Bank
High sea scallop abundances such as those in the closed areas of Georges Bank may cause predators, including sea stars, to aggregate and cause increased natural mortality rates for sea scallops. We hypothesized that sea stars are aggregated and are of larger size in areas of Georges Bank that are closed to fishing. Between 1999 and 2003, we systematically video surveyed 3809 stations (4 quadrats per station) in areas open and closed to fishing on Georges Bank. Sea stars were aggregated within the closed areas from 2000 to 2003. Sea star densities were higher in the closed areas than in the open areas during each year from 2000 to 2003. The average arm length of sea stars within the open areas was not always smaller or larger than those in the closed areas; however, average arm length estimates were influenced by the abundance of sea star recruits. Sea scallop densities were independent of sea star densities. Sea star predation influenced sea scallop densities in specific locations, as instantaneous natural mortality rates were high