Impacts of Scallop Dredging on Fish Habitat of Northeastern Georges Bank.  (Year 1 of 2) Project Number: NAGL-98-02A Principle Investigators: Collie, J. S., and P. C. Valentine Region(s): Northern Georges Bank Project Objectives: 1.To document the recovery of an area closed to fishing, compared with areas where bottom fishing continues. The null hypothesis is no difference in community composition between open and closed areas. 2.To measure the rate of recolonization of defaunated gravel placed in disturbed and undisturbed sites. To document the succession of epifaunal species as recolonization proceeds. The null hypothesis is that the rate of recolonization of clean gravel is the same at undisturbed and previously disturbed sites. The alternate hypothesis is that recolonization at previously disturbed sites will be slower because of the distance from the source of recolonizing individuals. 3.To compare the community structure of undisturbed habitats that are dominated by different epifaunal taxa (hydroids; bryozoans; Filograna worm colonies; sponges). The null hypothesis is that these epifauna represent different stages of succession. 4.To census scallops in areas with different fishing levels, ranging from: (1) undisturbed; (2) recovering; (3) moderately disturbed ; and (4) heavily disturbed. The null hypothesis is that scallop densities are highest on moderately disturbed habitats, with few competitors and predators. Summary of Research: 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 sea floor 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 undredged to dredged sites. Undredged sites have a higher abundance of organisms, biomass, and species diversity. Dredged sites have a higher evenness diversity, possibly because dredging prevents any species from becoming numerically dominant. Many of the species that are absent or less common at undredged sites are small, fragile polychaetes, shrimps and brittle stars. Undredged 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 dredged sites. Small fish are more abundant at undredged sites, the few species that were abundant 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 at least through 1999 and will continue to be a study site. The project objectives will be accomplished by analysis of video and still-photo imagery of the sea floor, 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 samplers 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 sea-bed habitats, to recover and deploy recolonization trays, to collect voucher specimens for species description and identification, and to conduct close-up photography of the sea bed. This project will describe and map essential fish habitat of groundfish and scallops, and evaluate the impact of bottom fishing gear (dredging and trawling). Research results will be used by managers and policy makers to assess the effects of sea-bed 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: A total of 11 submersible dives were made on the R/V EDWIN LINK cruise from 14 to 23 August 1998. Copies of the tapes are stored at NURC-NAGL, URI-GSO, and USGS. The slide film from the still camera has been developed and is being scanned to CD-ROM. Despite problems with the still camera (exposure, double film advance), usable photos were obtained. A subset of the slides will be printed and used to quantify the percent cover of benthic epifauna (6-10 photos randomly chosen from each transect). A USGS still camera was used on four of the submersible dives to take close-up photos of the sea bed from a height of 23cm. The photos show the sea bed and small attached and mobile organisms in excellent detail, and supplement data on species distribution and abundance normally collected by traditional bottom photos and dredging. A total of 28 drift video transects were made. Video tapes and 35-mm negatives are archived at the USGS, Woods Hole, MA. A first look at the videos indicates continued recovery of the benthos at Site 17 and a decreasing gradient in bottom cover moving from Site 17 to 17W. Thirteen Naturalists' dredge samples were taken at the sites of interest. These samples allow us to quantify the non colonial taxa and they provide voucher specimens of colonial taxa seen in the photographs. We used the same sampling and processing protocol that we developed on previous cruises. Sorting and identification of these samples has started at GSO-URI. ANOVA and multivariate methods are used to compare the megafaunal communities at different stations. We made 12 deployments of baited amphipod traps. Our priority this cruise was to compare the open and recovering areas at 40 m depth (Site 17W and Site 17) and to compare the disturbed and undisturbed areas at 80 m depth (Site 13 and 20). Three replicate traps were deployed at each site. The trap samples are sorted and the data have been entered into computer databases. Our sampling was coordinated with the NMFS scallop survey, which sampled Georges Bank the week before our cruise. Three stations were chosen to compare direct photographic estimates of scallop densities and size distributions with the scallop survey estimates. The R/V Albatross conducted three short tows at each of the three stations. We mapped the polygon defined by these tows and conducted photo surveys within this polygon in an effort to sample the same area as the scallop survey. Still photographs from one of these sites have been analyzed. Six sediment recolonization trays (SAMs) were deployed on our NURP cruise in summer 1997. The trays were deployed in two clusters of three replicates, one cluster at Site 17 and the other at Site 20. During the August 1998 cruise we were able to locate only one of the SAMS with the submersible because the submersible's sonar did not function. There was no sample in the sediment tray and the recovery line had been prematurely released from its canister and appeared to have been tangled. It is possible that this SAM had been struck by fishing gear. We are confident that we know the locations of the SAM trays and the ship's crew was able to find three of the six with the ship's fathometer. Another attempt to recover the SAM trays will be made in June 1999. Our visual impressions from this cruise are that the benthic community in Closed Area II (Site 17) continues to recover relative to open area to the west, which has a low diversity of benthic fauna (Site 17W). Erect sponges are particularly apparent in the closed area. Scallop densities in the Canadian zone (Site 16) appear to have declined since we surveyed this area with the ROV in 1996. We observed more evidence of fishing activity at the deep, undisturbed site in the Canadian zone (Site 20) which has always had the highest benthic diversity. We seem to be documenting the erosion of this complex habitat. Preliminary results from our ongoing study indicate recovery of the benthic megafauna (animals>5mm) in Closed Area II (Fig. 1). Site 17 is situated within the closed area and had the highest scallop dredging effort prior to the closure. Site 18, to the west of the closed area, had low dredging effort prior to the closure but may have had effort displaced to it following the closure. Prior to the closure the heavily disturbed Site 17 had lower abundance, biomass, and species diversity of benthic megafauna. Starting six months after the closure and continuing to 1997 we have measured significant increases in all three indices in the closed area compared with Site 18. These data are preliminary as the species lists have not been thoroughly compared between cruises. The 95% confidence intervals are wide because the means are based on just three replicates from stations that have been consistently sampled over time. Samples from additional stations in and outside the closed area will be added to the analysis. This first look at the data suggests that recovery of the benthic megafauna inside the closed area will take longer than three years. Samples from the 1998 cruise, not yet analyzed, will add another data point to the time series. Benefits: The northern edge of Georges Bank is an important habitat for sea scallops, Atlantic cod, and haddock. The average value of these fisheries during 1989-1993 was approximately $100 million for scallops, $50 million for cod, and $5 million for haddock. This research project is helping to fulfill the mandate of the Sustainable Fisheries Act by describing Essential Fish Habitat (EFH) and quantifying the impacts of bottom fishing on EFH. Results of our research were used by the New England Fisheries Management Council in preparing the omnibus EFH amendment, and specifically to designate a Habitat Area of Particular Concern on northern Georges Bank. Photographs taken with the MaxRover ROV were used by Steven Murawski to brief the Secretary of Commerce on closed area management. Photographs and results from our study (Fig. 1) were used by David Evans in a presentation to Administrator of NOAA, James Baker. Results of our study have been used by other stakeholders such as the Cape Cod Commercial Hook Fishermen's Association and the American Oceans Campaign. Bottom photographs and videos taken on NURP cruises are increasing public awareness of underwater habitats. Bottom photos from our 1997 cruise have been published in Science and the Boston Globe. A summary video from our 1998 cruise (copy enclosed) was used by the Public Media Center in San Francisco. Finally, this project is increasing the basic understanding of the impacts of disturbance on benthic communities. New Research Topics and Directions: A high-resolution side-scan sonar survey of part of Nantucket shoals and the Great South Channel was conducted by the USGS in fall 1998. We plan to take advantage of this survey to conduct habitat-specific sampling of this area in June 1998. Paired sites will be identified inside and outside of Closed Area I and sampled with photo transects and the Naturalists' dredge. To investigate the functional role of habitat complexity, my graduate student Jerome Hermsen, is planning to conduct predator-prey experiments in aquaria. He plans to quantify the relationship between habitat complexity and prey vulnerability for juvenile haddock with cod and silver hake as predators. This will not be part of our NURP project, but it is a spin-off of our habitat work. Leg 1    Begin Date: 8/15/1998   End Date: 8/22/1998   Support Vessel/Platform: R/V Edwin Link System Ops Days Dives Dive Time (hrs) Depth (m) Clelia 8 11 20.3 82 Keymap: Location of Project Dives: Legend: Clelia 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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