CETACEAN HIGH-USE HABITATS OF 

 THE NORTHEAST UNITED STATES CONTINENTAL SHELF 1 



Robert D. Kenney and Howard E. Winn 2 



ABSTRACT 



Results of the Cetacean and Turtle Assessment Program previously demonstrated at a qualitative level 

 that specific areas of the continental shelf waters off the northeastern U.S. coast consistently showed 

 high-density utilization by several cetacean species. We have quantified, on a multispecies basis and with 

 adjustment for level of survey effort, the intensity of habitat use by whales and dolphins, and defined 

 areas of expecially high-intensity utilization. The results demonstrate that the area off the northeast United 

 States, which is used most intensively as cetacean habitat, is the western margin of the Gulf of Maine, 

 from the Great South Channel to Stellwagen Bank and Jeffreys Ledge Secondary high-use areas include 

 the continental shelf edge and the region around the eastern end of Georges Bank. High-use areas for 

 piscivorous cetaceans are concentrated mainly in the western Gulf of Maine and secondarily at mid-shelf 

 east of the Chesapeake region, for planktivores in the western Gulf of Maine and the southwestern and 

 eastern portions of Georges Bank, and for teuthivores along the edge of the shelf. In general, habitat 

 use by cetaceans is highest in spring and summer, and lowest in fall and winter. 



From October 1978 through January 1982, the Ceta- 

 cean and Turtle Assessment Program (CETAP) at 

 the University of Rhode Island conducted surveys 

 of the waters of the U.S. continental shelf from Cape 

 Hatteras, NC, to the northern Gulf of Maine. The 

 purpose of these surveys was to provide data on the 

 distribution and abundance of whales, dolphins, and 

 sea turtles inhabiting the northeast shelf for input 

 to decision-making relative to offshore oil and gas 

 resource development. Twenty-six species of ceta- 

 ceans were observed during the study, and their 

 distributions have been described in some detail 

 (CETAP 1982). Each species exhibited a distinctive 

 pattern of distribution in space and time, inhabit- 

 ing some small portion(s) of the study area at higher 

 relative densities. 



When comparing distributions of individual 

 species, there appear to be specific geographic areas 

 which consistently contained higher abundances of 

 several cetacean species. This phenomenon had been 

 noted during the CETAP study (CETAP 1982), but 

 had not been analyzed quantitatively. An individual 

 species approach to the analysis of such multispecies 

 phenomena has certain limitations. One cannot 

 simply combine the sighting distributions of several 

 species; the different cetacean species vary widely 



'This report has been reviewed by the Minerals Management Ser- 

 vice and approved for publication. Approval does not signify that 

 the contents necessarily reflect the views and policies of the Ser- 

 vice, nor does mention of trade names or commercial products con- 

 stitute endorsement or recommendation for use 



2 Graduate School of Oceanography, University of Rhode Island, 

 Narragansett, RI 02882-1197. 



Manuscript accepted July 1985. 



FISHERY BULLETIN: VOL. 84, NO. 2, 1986. 



in size and may have quite different ecological 

 requirements. An additional complication in a study 

 of habitat use, based on sighting data, is introduced 

 by the uneven allocation of sighting effort. One can- 

 not be certain whether a lack of sightings is due to 

 absence of whales or absence of observers, or, con- 

 versely, whether a concentration of sightings repre- 

 sents a real concentration of whales or simply a con- 

 centration of effort. Thus it is difficult to simply or 

 directly combine single-species sighting distributions 

 in any sort of multispecies habitat use analysis. In 

 this paper, we have attempted to synthesize, from 

 the CETAP individual species sighting data, a mea- 

 sure of the intensity of habitat use by the total ceta- 

 cean fauna in the study area which accounts for both 

 interspecific differences and differences in allocation 

 of effort. These results then serve to delineate those 

 specific habitat areas which are used at particularly 

 high levels by whales and dolphins off the north- 

 eastern United States. 



An underlying assumption in this paper is that a 

 habitat which is occupied by whales or dolphins is 

 necessarily utilized by them. Previous results from 

 CETAP data have shown that the distribution of 

 sightings of a particular species where definite 

 feeding behavior was observed tended to closely mir- 

 ror the overall sighting distribution for that species. 

 Only feeding activity at or very near the surface can 

 be seen by observers on ships or airplanes, but much 

 feeding behavior likely occurs below the surface For 

 some species, observations of surface feeding are 

 very rare. In addition, cetaceans are large mammals 



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