Impact of limited short-term sea scallop fishery on epibenthic community of Georges Bank closed areas

Abstract

On Georges Bank, 2 areas that had been closed to sea scallop fishing since 1994 were opened for a limited harvest from August 2000 to February 2001. The effects of this limited short-term fishery on the epibenthic community were examined using a 'before/after, control/impact' environmental design conducted with video surveys. A centric systematic survey with 1379 stations placed on a 1.57 km grid, with 4 video quadrats collected at each station (3.235 m 2 per quadrat equaling 17 789 m 2 total sample area), was completed in 2 control and 2 impact areas before and after the fishery. The sea scallops Placopecten magellanicus and starfishes (primarily Asterias vulgaris) comprised more than 84% of the fauna. Changes in the number of taxonomic categories and the density of individuals within each category in the areas impacted by the fishery were similar to changes in the control areas that remained closed to fishing. Further, sediment composition shifted between surveys more than epibenthic faunal composition, suggesting that this community is adapted to a dynamic environment. The limited short-term sea scallop fishery on Georges Bank appeared to alter the epibenthic community less than the natural dynamic environmental conditions.

Effect of closed areas on populations of sea star Asterias spp. on Georges Bank

“…Portions of CAIIS, NLCA, and CAI were opened from 1999 to 2000, in 2000, and from 2000 to 2001, respectively, for a short-term limited fishery (NMFS 1999-2001, Stokesbury & Harris 2006. Sea stars were aggregated in closed areas and in some cases densities decreased after a fishing event.…”

Sea scallop mass mortality in a Marine Protected Area

“…The shell heights from 2004 were projected to the time of the 2005 survey using the VBGF parameters for GSC sea scallops and assumed no growth for scallops greater than the mean maximum asymptotic size, H ∞ = 155 mm (our Eq. 4, Harris & Stokesbury 2006). We subtracted the observed scallop shell height frequency in 2005 from the predicted shell height frequency to estimate which sizes suffered the greatest mortality.…”

“…The growth increment was estimated with the von Bertalanffy growth function (VBGF): (4) where H t (mm) = scallop shell height at time t (yr), t 0 = theoretical time when H is zero, and k (yr -1 ) is the rate at which shell height approaches the mean asymptotic size H ∞ (mm) (Beverton & Holt 1957). We applied the VBGF parameters H ∞ = 155 mm, k = 0.33 yr -1 for the GSC and set t 0 = 0.5 yr to roughly correspond with initial shell growth after settlement in late autumn (Harris & Stokesbury 2006). F was calculated using Baranov's catch equation (Ricker 1975) recast as: (5) where C = number of scallops harvested.…”

“…1). To capitalize on this high density, a short-term fishery was permitted access and harvested 584 t between 15 August and 31 October 2000 (Stokesbury & Harris 2006 To evaluate the population dynamics of scallops in the NLCA MPA, we conducted annual video surveys. We hypothesized that scallop abundance in the NLCA would decline due to several factors: (1) a substantial proportion of the scallops were large and old (Stokesbury 2002, Stokesbury et al 2004); (2) there was limited recruitment into the area (Stokesbury et al 2004); (3) scallop abundance tends to fluctuate in a cyclic pattern (Dickie 1955, Caddy 1989; and (4) mass mortalities have occurred historically (Dickie & Medcof 1963).…”

Quantifying sea scallop bed diameter on Georges Bank with geostatistics

“…1). These surveys employed a two-stage design, in which four random quadrats were sampled at each node (station) of a systematic grid (Stokesbury, 2002;Stokesbury and Harris, 2006;Stokesbury et al, 2007). Data from these surveys were used to characterize the spatial structure of sea scallop beds in the NE and NL.…”