Georges Bank Benthic Habitat Studies:
Effects of Bottom Fishing on Georges Bank
About this project. In order to gain a better understanding of how bottom fishing impacts benthic organisms, a team of researchers from the University of Rhode Island's Graduate School of Oceanography (GSO) and the U.S. Geological Survey (USGS) set out in 1994 to survey the benthic megafaunal community of Georges Bank. This project's study area was confined to the gravel habitat that straddles the boundary between the U.S. and Canadian exclusive economic zones (EEZs). This area was selected because previous research has indicated that it serves as an important nursery for juvenile cod (Gadus morhua) and haddock (Melanogrammus aeglefinus).1 Within this region, trawl marks appearing in side scan sonar images were counted in order to identify sites with different levels of bottom fishing disturbance. Based on this information, six study sites were pinpointed and classified as either “disturbed” or “undisturbed”. At these sites, benthic dredge samples have been collected on a nearly annual basis. In addition, photographs and videos of the sea floor have been recorded using the SEABOSS system, remotely operated vehicles (ROVs), and manned submersibles. Data from this project have revealed significant differences between disturbed and undisturbed sites in terms of abundance, biomass, species diversity, and benthic community structure.
In December 1994, three large sections of Georges Bank, comprising an area of 17,000 km2, were closed to all types of fishing gear capable of retaining groundfish.2 Since one of our most disturbed study sites was located within a closed area, this event provided a unique opportunity to investigate the changes that occur as a benthic ecosystem recovers from chronic fishing impacts.
About Georges Bank. Located along the eastern edge of the Gulf of Maine between Cape Cod and Nova Scotia, Georges Bank is a submarine bank that was formed through the erosion of glacial sediments. Due to the continuous provision of nutrients via tidal mixing, Georges Bank is among one of the most biologically productive marine areas on the eastern seaboard. This high level of primary production supports a large fishery that is centered around the bank. In 2002, New England commercial fish landings were valued at $685 million dollars.3 Much of this catch originated from Georges Bank.
Despite its high productivity, by the early 1990s several of the area's commercially important fish stocks were showing signs of decline. Overfishing and the degradation of essential fish habitat (EFH) are among some of the proposed explanations for the reduced stock size of Georges Bank fish populations. Much of the damage affecting EFH has been linked to bottom fishing using otter trawls and scallop dredges. Between 1984 and 1990, it was estimated that the area trawled on Georges Bank was equivalent to three times the area of the bank itself.4 In order to foster the recovery of fish stocks, approximately 25 percent of the bank was closed to bottom fishing in 1994. Initial results of scientific studies examining these closed areas have revealed several promising signs of recovery. Spawning stock biomass of cod, haddock, and yellowtail flounder (Limanda ferruginea) has risen since the establishment of the closed areas.5 Even more dramatically, the biomass of sea scallops (Placopecten magellanicus) has increased 14-fold within unfished areas.6 The information presented in this website will demonstrate that the designation of the Georges Bank closed areas has also positively impacted benthic megafaunal species, which provide food and habitat for commercially important fishes.