Complex habitat boosts scallop recruitment in a fully protected marine reserve

This study investigated the effects of a fully protected marine reserve on commercially valuable scallops and benthic habitats in Lamlash Bay, Isle of Arran, United Kingdom. Dive surveys found the abundance of juvenile scallops to be greater within the marine reserve than outside. A novel multivariate approach, based upon neural networks and generalised linear models, revealed the greater abundance of juveniles to be related to the greater presence of macroalgae and maerl within the reserve boundaries. This complex habitat appeared to have positively encouraged spat settlement. In contrast, the density of adult scallops did not differ between the two treatments, possibly due to the short duration of protection. However, the age, size and biomass of adult scallops were significantly greater within the reserve. Overall, this study suggests that the newly created marine reserve is already providing benefits which are flowing back to species targeted by fisheries, emphasising the importance of marine reserves in ecosystem-based management of fisheries. Introduction Closing areas to some or all types of fishing through the implementation of marine protected areas (MPAs) and marine reserves is becoming an increasingly utilised management tool to conserve marine biodiversity, ecosystem services and fisheries resources (Gell and Roberts 2002; Adams et al. 2010; Halpern et al. 2010; Unsworth et al. 2010). The rising interest in MPAs and marine reserves is supported by a growing number of scientific studies that have shown that closed area protection can increase the abundance and mean size of target species (Halpern and Warner 2002; Halpern 2003), enhance local reproductive output (Roberts and Hawkins 2000; Roberts et al. 2001; Gaines et al. 2003; Grantham et al. 2003) and improve the survival and growth of juveniles (Myers et al. 2000; Beukers-Stewart et al. 2005). All of these effects may result in the greater production of larvae, juveniles and adults which then disperse to grounds outside the closed area and contribute to fishery landings (McClanahan and Mangi 2000; Gell and Roberts 2003). The growing use of MPAs and marine reserves as a fisheries management tool has co-occurred with a paradigm shift in fisheries management; with perspectives shifting from traditional single-species management to more holistic approaches where management priorities begin with the ecosystem rather than the target species (Pikitch et al. 2004; Zhou et al. 2010). The aim of such ‘ecosystembased fishery management’ is to sustain healthy marine ecosystems and the fisheries they support by addressing some of the unintended consequences of fishing, such as the mortality of non-target organisms and the physical impacts of fishing gears (Link 2002; Zhou et al. 2010, Stokesbury et al. 2011). Theory suggests that integrating ecosystem level concerns into fishery management will Communicated by S. D. Connell. L. M. Howarth B. D. Beukers-Stewart (&) Environment Department, University of York, Heslington, York YO10 5DD, UK e-mail: [email protected] H. L. Wood Community of Arran Seabed Trust, Allt-na-ceirde, Whiting Bay, Isle of Arran KA27 8QT, UK A. P. Turner Department of Electronics, University of York, Heslington, York YO10 5DD, UK