Stellwagen Bank Final EIS and Management Plan 



Page 29 



orcas consume a variety of fishes including tuna, 

 herring and mackerel, and have also been known to 

 attack pinnipeds, seabirds, and other cetaceans. 



White-sided dolphins (Lagenorhynchus acutus : 7 to 

 9 feet, or 2.2 to 2.7 meters in length) are 

 widespread throughout the Gulf of Maine/Georges 

 Bank environment all year, and are particularly 

 abundant in the southwestern portion of the Gulf 

 (incorporating Stellwagen Bank). These highly 

 social cetaceans are found only in the North 

 Atlantic, and are generally present on northern 

 portions of the Bank and on Jeffreys Ledge at all 

 times of the year. They are frequently seen feeding 

 with fin whales, and may also be seen bow-riding 

 fins or humpbacks, as well as vessels. Pods of 

 white-sided dolphins may range in size from 10 to 

 over 1,000 animals, although most groups number 

 between 25 and 150. Calves are also observed in 

 this area throughout the year. Prey species include 

 a variety of fishes, such as herring, hake, smelt, 

 capelin, cod, and squid. 



White-beaked dolphins (Lagenorhynchus albirostris : 

 8 to 10 feet, or 2.4 to 3.0 meters in length), like the 

 white-sided dolphins, are found only in the North 

 Atlantic; although they generally follow a more 

 northerly range, from Cape Cod to Greenlcuid. 

 White-beaked dolphins are considered casual 

 visitors to the northern end of Stellwagen Bank, 

 where sightings usually occur between April and 

 November. While in the Gulf of Maine, white- 

 beaked dolphins likely feed on sand eels; squid may 

 also be consumed. In the 1950's, white-beaked 

 dolphins were more abundant in the overall Gulf of 

 Maine; they have been displaced by increased 

 numbers of white-sided dolphins. 



Harbor porpoises (Phocoena; 4 to 6 feet, or 1.2 to 

 1.8 meters in length) are locally abundant in 

 temperate waters of the Bay of Fimdy and the 

 northern Gulf of Maine during summer months. 

 The species exhibits seasonal patterns in spatial 

 distribution within this general region, and is 

 particularly concentrated in the southwestern Gulf 

 of Maine, the Great South Channel, Jeffreys Ledge, 

 and coastal Maine during mid-spring months. 

 Sightings are generally recorded from south of Cape 

 Cod north to the Bay of Fundy during spring 

 months. Following April, harbor porpoises are 



only rarely seen in Cape Cod waters, and the 

 decrease in sighting frequency suggests a general 

 northeast movement toward the northern Gulf of 

 Maine and Bay of Fundy. (Cited in T. Bigford, 

 NMFS/NER, AprU 1991). 



The summer population estimate of 

 approximately 16,000 harbor porpoises in the Gulf 

 of Maine is considered somewhat unreliable, due to 

 seasonal changes in species distribution, which make 

 survey consolidation difficult. The Northeast 

 Fisheries Center of NMFS planned a summer 1991 

 survey of harbor porpoise, which should produce 

 more reUable population estimates. (T. Bigford, 

 NMFS/NER, April 1991). Harbor porpoise diet 

 consists primarily of small schoohng fishes, 

 polychaetes, and cephalopods. In the Gidf of 

 Maine, likely prey species include mackerel, herring, 

 squid, and sand eel. 



A number of harbor porpoises annually are 

 entangled and killed incidentally in both U.S. and 

 Canadian gillnet fisheries in the Gulf of Maine. 

 Although reliable estimates of affected harbor 

 porpoises in the U.S. fishery do not exist at this 

 time, the possibility exists that the species may be 

 declining due in part to entanglement losses. (T. 

 Bigford, NMFS/NER, April 1991). Through the 

 Marine Mammal Exemption Program, (§ 114 of 

 MMPA) and the gillnet industry, NMFS is currently 

 seeking to assess and rectify this problem. 



Bottlenose dolphins (Tursiops truncatus ; 8 to 12 

 feet, or 2.4 to 3.7 meters in length) are occasionally 

 seen in the Gulf of Maine during the late summer 

 and fall. This species, generally occurring offshore 

 along shelf areas from Cape Hatteras (North 

 Carolina) to Georges Bank is the larger of two 

 recognized forms of Tursiops truncatus . (The 

 smaller form occurs more frequently in inshore 

 areas of the mid-Atlantic south of Delaware Bay.) 

 While in the Gulf of Maine, bottlenose dolphins 

 feed opportunistically on a wide variety of fish, 

 squid, and invertebrates. 



Common (or Saddleback) dolphins (Delphinus 

 delphis ; 6 to 8 feet, or 1.8 to 2.4 meters in length) 

 are occasional visitors to the Gulf, particularly in 

 the fall and winter. Saddlebacks are generally seen 

 over northeastern portions of Georges Bank, 



