Ecology of the Northeast US Continental Shelf
Special considerations are required for species that are threatened or endangered by human activities even when these species are not directly targeted by the fisheries and other stressors. Legal mandates and authorities for protection of these species fall primarily under the Marine Mammal Protection Act, the Endangered Species Act, and other pieces of legislation including the Magnuson-Stevens Fishery Conservation and Management Act and the Migratory Bird Treaty Act of 1918.
Among the important threats facing protected resource species at sea are incidental takes in fishing gear. Observations of by-catch of non-target and protected resource species in commercial fisheries show that sea birds composed the largest fraction of captures in terms of numbers, followed by sea turtles and dolphins. While whales accounted for the smallest fraction. Strategies for reducing incidental capture of each of these groups remains a principal focus of research at the interface between fisheries and conservation biology of protected species.
Marine mammal species listed as endangered that occur in the Northeast U.S. Continental Shelf Large Marine Ecosystem (NES LME) include the blue, humpback, North Atlantic right, fin, sei and sperm whales. The status of the western North Atlantic right whale is of particular concern (see Figure 1). This population is thought to number around 400 individuals. They are highly susceptible to both collisions with ships and entanglement in fixed fishing gear, resulting in serious injuries and deaths. Current efforts to reduce these risks include sighting surveys for whales during times when they are congregated, wide dissemination of whale locations to mariners, restrictions on the configurations of fixed gill net, lobster and other pot gear, deployment of disentanglement teams, and support for researchers working on new gear and sensing technologies that could further reduce these risks.
Other marine mammal species have increased markedly. For example, harbor seals increased dramatically over the last decade with potentially important implications for the ecosystem. Harbor seals prey on fish species and in some areas, conflict has arisen over the predation by seals on commercially important fish species.
Five species of threatened or endangered sea turtles can be found in the NES LME including green, hawksbill, Kemp’s ridley, leatherback (Figure 2), and loggerhead turtles. Threats to sea turtles include disruption of nesting sites, incidental capture in fishing gear, and ship collisions. The latter two impacts are of concern for species occurring in the NES LME.
The distribution of many sea turtles follows well-defined oceanographic features, including fronts associated with the Gulf Stream. These fronts are also important habitat for large pelagic fishes, and there are consistent spatial patterns of incidental takes of sea turtles in the longline fishery off the edge of the shelf. These takes have been substantially reduced both through closures and development of modified hooks.
For more information, go to our "Sea Turtles" page.
The National Marine Fisheries Service's marine stewardship role also includes responsibility for the protection of seabirds and other migratory birds. This responsibility is supported by both domestic and international directives to gain a better understanding of seabird bycatch and ways of reducing incidental takes of seabirds. Seabirds were historically hunted for food and for plumage and many species declined precipitously due to over-exploitation. By-catch in fishing operations and threats to nesting areas for some species are currently of greatest concern. The species with the largest number of takes are shearwaters (Figure 3) and petrels followed by loons and gulls. The fisheries that were most responsible for these bycatches were bottom otter trawls and scallop dredges, followed by the drift gillnet and finally the midwater paired otter trawl. This situation differs markedly from the by-catch issues in the Pacific, where longlines are a major problem.
For more information, go to our "Seabirds" page.