Impacts of Scallop Dredging on Fish Habitat of Northeastern Georges Bank.  (Year 2 of 2) Project Number: NAGL-98-02B Principle Investigators: Collie, J. S., and P. C. Valentine Region(s): Northern Georges Bank / Canadian Waters, Northern Georges Bank / U.S. Waters, SSA 13 (Disturbed area in Canadian zone), SSA 17 (Closed Area II), SSA 17W (Open area at the same depth), SSA 20 (Undisturbed area in Canadian zone) The proposed research is part of a multi-year study of the effects of bottom fishing on benthic megafaunal communities and fish habitat found on the gravel seafloor of northeastern Georges Bank. Studies were initiated in 1994 with support from NMFS and have continued in 1996 and 1997 with support of NURP. Our studies to date have revealed a gradient in community structure from undisturbed to disturbed sites. Undisturbed sites have a higher abundance of organisms, biomass, and species diversity. Disturbed sites have higher evenness diversity, possibly because dredging prevents any species from becoming numerically dominant. Many of the species that are absent or less common at disturbed sites are small, fragile polychaetes, shrimps and brittle stars. Undisturbed sites also are characterized by the presence of colonies of hydrozoans, bryozoans, and the tube-dwelling polychaete Filograna implexa. This epifauna provides a complex habitat for small, mobile animals that is almost entirely absent at disturbed sites. Small fish are more abundant at undisturbed sites; the few species that are abundant at the disturbed sites are mainly predators and scavengers. Our most heavily disturbed study area has been closed to fishing since December 1994 and provides an excellent opportunity to document the recovery and succession of the benthic fauna. Observations in 1996 and 1997 indicate the closed area is beginning to recover as evidenced by the widespread presence of new colonies of hydrozoa and bryozoa, and an increase in the population of juvenile scallops. The closed area will remain closed for the foreseeable future and will continue to be a study site in 1998 and 1999. Objectives of this research are: (1) to document the recovery of an area closed to fishing compared with areas where bottom fishing continues; (2) to measure the rate of recolonization of defaunated gravel placed in trays in disturbed and undisturbed sites, and to document the succession of epifaunal species as recolonization proceeds; (3) to compare the community structure of undisturbed habitats that are dominated by different epifaunal taxa (hydroids; bryozoans; Filograna worm colonies; sponges) and determine if they represent different stages of succession; and (4) to census scallops in areas with different fishing levels to determine if scallop densities are highest on moderately disturbed habitats, with few competitors and predators. The objectives will be accomplished by analysis of sidescan, video, and photo imagery of the seafloor, and of samples collected by biological dredges, baited traps, and recolonization trays. The gravel pavement on northeastern Georges Bank is difficult to sample with conventional grab samples and box corers. Therefore we use a variety of complementary sampling methods. A submersible or ROV will be used to conduct photo/video transects of the seabed habitats; to recover and deploy recolonization trays; to perform suction sampling to collect small invertebrates and fish that are difficult to sample with the biological dredge; to collect voucher specimens for species description and identification; and to conduct close-up photography of the seabed. This project will describe and map essential fish habitat and evaluate the impact of fishing gear (dredging and trawling) on a traditional groundfish and scallop fishery. Research results will be used by managers and policy makers to assess the effects of seabed disturbance on benthic habitats in an important fishery region, and to determine management strategies which may include monitoring, closures and research. These results will provide a basis for further research and will stimulate new approaches to the study of benthic fish habitats.   Results: In June 1999 we conducted a two-vessel cruise to study the gravel habitats on Georges Bank. Having two vessels and good weather allowed to accomplish almost all our cruise objectives, and to sample a total of 110 stations. It was also the first offshore cruise for the R/V Connecticut. During the cruise we collected dredge samples and made photographic surveys to compare the benthic communities at undisturbed, disturbed, and recovering sites. These samples are still being analyzed in the laboratory. When completed, they will extend our times series of recovery data from the closed areas to 5 years. We completed trapping of scavenging amphipods and isopods and have made preliminary analysis of the results. Unlike the previous three years, the density of scavenging amphipods and isopods was higher at the disturbed than the undisturbed sites. With the help of expert ROV pilot, Jamie Sherwood, we recovered 3 of 6 settling trays that had been deployed in 1997. The ROV was used to cut the release mechanism and to ensure that the retrieval line extended to the surface. The trays were then recovered by the R/V Connecticut. All three trays contained samples that will be used to measure the recolonization rate of defaunated gravel. The successful recovery of these settling trays was due to the skill and cooperation of the crews of the R/V Abel J and R/V Connecticut. Three of the ROV transects were designated as scallop transects to photographically survey scallop abundance. Unfortunately, the NMFS was unable to follow-up and make tows with the survey scallop dredge at the same locations because of mechanical failures. Benefits: The main benefit of this research is the characterization and protection of essential fish habitat (EFH). The gravel pavement areas on Georges Bank are EFH for sea scallops and groundfish, especially juvenile cod and haddock. Our work has quantified the impacts of bottom fishing on the benthic community of these gravel habitats. Based in part on our results, part of the gravel pavement on northern Georges Bank was designated a Habitat Area of Particular Concern for juvenile cod (this area contains our dive locations 4,5,6,8,9,10 and 12 from 1999). By sampling in the closed areas and by deploying settling trays we are measuring the rate at which the benthic community can recover from disturbance. This recovery rate is an essential piece of information for designing and evaluating rotational harvest strategies for sea scallops. If the recovery time exceeds the rotation period, the habitats may remain in a permanently disturbed state. Through a pilot study, we were able to demonstrate the possibility of measuring the abundance and size distribution of sea scallops with photographic surveys. Owing to technical difficulties we were able to make only limited comparisons with the NMFS trawl survey. The differences in density estimates between the NMFS dredge and our photographic transects imply a dredge efficiency between 20% and 70%. New Directions: Our prior research has concentrated on northeastern Georges Bank. In fall 1998 a detailed bathymetric map was made for USGS of the Great South Channel Area. We took advantage of this map to begin site-specific sampling of the Great South Channel Area in 1999. Important fish habitat is contained within this area. In cooperation with the NMFS we have proposed to extend this research by investigating the potential link between habitat disturbance and fish production. Several approaches will be used, including measuring the habitat-specific distribution of juvenile cod. We continue to investigate the development of sampling devices that will operate in the high current regimes of Georges Bank. Leg 1    Begin Date: 6/15/1999   End Date: 6/25/1999   Support Vessel/Platform: R/V Able J System Ops Days Dives Dive Time (hrs) Depth (m) KRAKEN (MAXrover MKI) 8 14 17.24 84.43   Leg 2    Begin Date: 6/17/1999   End Date: 6/25/1999   Support Vessel/Platform: R/V Connecticut Keymap: Location of Project Dives: Legend: KRAKEN (MAXrover MKI) Hughes, E. 1999. Spatial characteristics of Atlantic sea scallops (Placopecten magellanicus) on northern Georges Bank". M.S. Thesis. University of Rhode Island. Hermsen, J.M. 2002. Effects of mobile fishing gear on the benthic megafauna and production of Georges Bank. Ph.D. Dissertation, University of Rhode Island.

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