Estimation of Sea Scallop Abundance in Closed Areas of Georges Bank, USA

The dispersion and settlement of sea scallop larvae spawned on Georges Bank (GB) and in the Great Southern Channel (GSC) were explored using an individual-based population dynamics model. The model consisted of 4 pelagic life stages (egg, trochophore, veliger, and pediveliger) and 3 benthic life stages (juvenile, young adult, and adult). It was driven by the 1995 to 2005 hindcast flow field predicted by the Finite Volume Coastal Ocean Model (FVCOM) in the Gulf of Maine (GOM), with spawning stocks specified by field survey data. In 1998In , and 2005, a large amount of larvae drifted southward along the shelf break to the Middle Atlantic Bight (MAB). The potential for long-distance southward transport of larvae was dependent on the upstream flow conditions on the Nova Scotian Shelf, climate forcing, and the timing and location of spawning on GB. The model also predicts considerable larval exchange between the GB and the GSC subpopulations, with 83% of larvae settled in the GSC being spawned on GB, and 46% of larvae settled on GB being spawned in the GSC on average from 1995 to 2005.

Section: Long-distance Transport Of Larvae From Gb To Mabmentioning

confidence: 99%

Modeling the connectivity between sea scallop populations in the Middle Atlantic Bight and over Georges Bank

Tian¹,

Chen²,

Stokesbury³

et al. 2009

“…The best documented example of this is from the Georges Bank fishing grounds off the NE coast of the USA (Murawski et al 2000, Myers et al 2000, Stokesbury 2002, Hart 2003, Stokesbury et al 2004. Three large areas on these grounds were closed to fishing in 1994 and after 4 yr of protection the sea scallop Placopecten magellanicus biomass (total and harvestable) was 9 and 14 times higher, respectively, in the closed than in the open areas (Murawski et al 2000).…”

Section: Introductionmentioning

confidence: 99%

Benefits of closed area protection for a population of scallops

Stewart¹,

Vause²,

Mosley³

et al. 2005

Despite the current interest in using closed areas for fisheries management, few studies have actually examined the benefits for invertebrate fisheries such as scallops. This study details the dynamics of a population of great scallops Pecten maximus (L.), within a closed area and an adjacent fished area off the Isle of Man, over a 14 yr period (1989 to 2003). Scallop densities were very low in both areas when the closed area was set up, but increased at an accelerated rate over time within the closed area. Scallop densities also increased on the adjacent fishing ground, but not to the same extent. Consequently, the density of scallops above the minimum legal landing size (110 mm SL) was more than 7 times higher in the closed area than in the fished area by 2003. There was also a shift towards much older and larger scallops in the closed area and, correspondingly, lower estimates of total mortality. Experimental dredging of 2 plots within the closed area confirmed that fishing drove these differences in population dynamics and structure. These patterns of scallop density, age and size structure resulted in the exploitable biomass (adductor muscle and gonad) of scallops being nearly 11 times higher in the closed area than in the fished area by 2003, and the reproductive biomass was 12.5 times higher. This is significant for fisheries management because the build up of high densities of large P. maximus individuals enhanced local reproductive potential and therefore the likelihood of export of larvae to the surrounding fishing grounds. Along with these direct benefits of closed area protection, juvenile scallops had higher survival and individual growth rates in the closed area, apparently in response to reduced fishing disturbance. Although juvenile scallops are not subject to direct removal by fishing, protection during this critical phase therefore appeared to assist the recovery of the closed area population. In summary, this study joins a growing number indicating that the use of closed areas offers a range of benefits over more traditional methods of managing fisheries. Fisheries for relatively sedentary and long-lived species such as P. maximus appear to be particularly suitable for this type of management.

“…The video survey was primarily designed to examine the distribution and abundance of sea scallops (Stokesbury 2002, Stokesbury et al 2004); however, a secondary goal was to observe the distribution and abundances of other macroinvertebrates, including sea stars. Survey stations were positioned using a centric systematic design, as it is simple and samples evenly across the entire survey area (Krebs 1999, Stokesbury 2002 ) on a grid with 5.60 km between stations ( Fig. 1, Stokesbury et al 2004).…”

Section: Methodsmentioning

confidence: 99%

“…The total area surveyed within each sample area varied temporally (Table 1). The precision of this survey design ranged from 5 to 15% for the normal and negative binomial distributions, respectively, for sea scallop densities assessed in the Nantucket Lightship Closed Area (NLCA) in 1999 (Stokesbury 2002).…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

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

Marino¹,

Juanes²,

Stokesbury³

2007

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. 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.