Recovery of a temperate reef assemblage in a marine protected area following the exclusion of towed demersal fishing

Abstract

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.

Figure 1. Locations of sites in Lyme Bay.

Some symbols overlap at this scale.

Figure 2. Univariate diversity measures to assess benthic recovery a) Species richness (mean m⁻² ± SE) and b) Total abundance of all taxa within frame grabs, (mean m⁻² ± SE), over time (2008, 2009, 2010, 2011) and treatment type (CC  =  closed control, NC  =  new closure, NOC  =  near open control, FOC  =  far open control).

Figure 3. nMDS plot illustrating similarities in assemblage composition between Treatments (averaged for site within treatment), (closed control  =  filled black triangles, new closure  =  filled grey triangles, near open control  =  open circle, far open control  =  open square), over time (2008, 2009, 2010 and 2011).

Data were dispersion weighted and square root transformed. Trajectories over time are indicated with lines from 2008 to 2011 for each treatment.

Figure 4. Relative abundance of sessile indicator species (mean m⁻² ± SE) per treatment (CC  =  closed control (black triangle), NC  =  new closure (grey triangle), NOC  =  near open control (white circle), FOC  =  far open control (white square), per year (2008, 2009, 2010, 2011) identified through frame grabs.

Figure 5. Relative abundance of sessile indicator species (mean m⁻² ± SE) per treatment (CC  =  closed control, NC  =  new closure, NOC  =  near open control, FOC  =  far open control), per year (2008, 2009, 2010, 2011) identified through video transects.

Figure 6. Relative abundance (mean m⁻² ± SE) of mobile indicator species per treatment (CC  =  closed control, NC  =  new closure, NOC  =  near open control, FOC  =  far open control), per year (2008, 2009, 2010, 2011).