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North Atlantic Right Whale

The most endangered large whale off the east coast of the United States is the North Atlantic right whale (Figs. 1 and 2). Although a great deal has been learned about this species and such information will aid in its recovery, many questions remain. The population presently numbers about 300, and its growth rate has been estimated at 2.5%, a rate lower than that for right whale populations in the Southern Hemisphere (Knowlton et al. 1994).



Fig. 1. The North Atlantic right whale is the most endangered whale off the U.S. Atlantic coast. Courtesy S. Landry, New England Aquarium, Boston

North Atlantic right whales move from wintering and calving grounds in coastal waters of the southeastern United States to summer feeding, nursery, and mating grounds in New England waters and in waters northward to the Bay of Fundy and the Scotian Shelf. Long-distance movements as far north as Newfoundland, the Labrador basin, and southeast of Greenland have been reported and suggest an extended range--at least for some individuals--and habitat areas not presently well described. Likewise, while a calving and wintering ground is described for coastal waters of the southeastern United States, 85% of the population is unaccounted for during the winter season, and perhaps 30% is unaccounted for during the summer feeding and nursery season. Sightings from the Gulf of Mexico suggest that the range of this species may be more extensive than previously believed (Blaylock et al. 1995).

Fig. 2. North Atlantic right whale mother and calf, 17 January 1992, just north of Daytona Beach, Florida. Right whales calve in coastal waters during December and January.
Courtesy S. L. Ellis, Sea World airship

Research suggests five major habitats or congregation areas for western North Atlantic right whales: southeastern U.S. coastal waters, the Great South Channel, Cape Cod Bay, the Bay of Fundy, and the Scotian Shelf. However, the results from satellite tracking studies suggest that movements within and between habitats and within regions may be more extensive than previously thought. Based on results from satellite-tracked animals, sightings of individuals made perhaps two weeks apart cannot be assumed to indicate a stationary or resident animal. Rather, movement data have shown rather lengthy and somewhat distant excursions within a few weeks within a season (Mate et al. 1992). These findings cast new light on the extent of movements and habitat use by right whales and raise new questions about the purpose and strategies for such excursions.

   

New England waters are a primary feeding habitat for the North Atlantic right whale, where it appears to feed primarily on calanoid copepods. These dense zooplankton patches are likely a primary component of the spring, summer, and fall right whale habitat (Kenny et al. 1986). During the peak feeding season in Cape Cod and Massachusetts bays, the acceptable surface copepod resource is limited to perhaps 3% of the region. Although feeding in the coastal waters off Massachusetts has been better studied, feeding by right whales has also been observed over Georges Bank, in the Gulf of Maine, in the Bay of Fundy, and over the Scotian Shelf. The characteristics of acceptable prey distribution in these areas are not as well known as those for the area off Massachusetts. New England waters also serve as a nursery for calves and, in some cases, as sites for mating.

   

Genetic analyses of tissue samples are providing insights to population definition. Schaeff et al. (1993) have suggested that western North Atlantic right whales probably represent a single breeding population that may be based on three female lines of descent. Genetics also suggests that, in addition to nursery areas in New England waters and in the Bay of Fundy, there exists somewhere an additional and undescribed summer nursery area used by approximately one-third of the population. A related question is where individuals other than calving females and a few juveniles overwinter, as one or more major wintering and summering grounds remain to be described for this animal.

   

The western North Atlantic right whale population in 1992 was estimated, from a census using photoidentification techniques, to be 295 individuals. This population may have been as small as 50 or fewer animals at the turn of the century, suggesting that it is now showing signs of slow recovery. Approximately one-third of all right whale deaths are caused by humans. Further, their small population size and low annual reproductive rate suggest that human sources of mortality may have a greater effect relative to population growth rates than they do for other whales. The principal factors believed to be retarding growth and perhaps population recovery for North Atlantic right whales are ship strikes and net entanglement in fishing gear (Kraus 1990). This population is considered to be small relative to its optimal size, and the species is listed as endangered under the U.S. Endangered Species Act. A recovery plan has been published and is in effect, though not completely implemented (National Marine Fisheries Service 1991). The total level of human-caused mortality and serious injury is unknown, but it has exceeded two right whales per year since 1990.

   
  Author
James H. W. Hain
National Marine Fisheries Service
National Oceanic and Atmospheric Administration
Northeast Fisheries Science Center
166 Water Street
Woods Hole, Massachusetts 02543

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