Stellwagen Bank Final EIS and Management Plan 



Pc^e28 



between 3,590 and 6,300 individuals (NMFS, 1991); 

 and the worldwide population is roughly estimated 

 at about 120,000. 



Sei whales (Balaenoptera borealis : 25 to 50 feet, or 

 7.6 to 15.2 meters in length) are smaller and darker 

 than fin whales, but difficult to identify. Sei whales 

 were first positively observed feeding in the 

 Stellwagen Bank area in 1986; and the numbers 

 recorded since then have been relatively low. They 

 feed exclusively on zooplankton, primarily copepods 

 and euphausiids (and krill in other feeding habitats). 



There are no recent population estimates for sei 

 whales in the North Atlantic. NMFS has estimated 

 approximately 4,000 individuals may be present in 

 this overall area. (NMFS, 1991). In 1988, 

 approximately 40 individual sei whales were 

 photographically identified at Stellwagen Bank; 

 however, a greater number were present. 



Blue whales (Balaenoptera musculus : 25 to 100 feet, 

 or 7.6 to 30.5 meters in length) are the largest 

 mammals on Earth. The first documented sighting 

 of a blue whale on the east coast of the United 

 States was recorded in October 1986 on the western 

 edge of Stellwagen Bank. Two additional sightings 

 of blue whales were recorded at the Bank in 1987. 

 In all instances, the whales were observed feeding, 

 probably on euphausiids. Blue whales may also 

 occasionally feed on copepods, fish, and squid. 



Although blue whales have been seen regularly 

 during summer months in the Gulf of St. Lawrence, 

 and around southern and northern Newfoundland, 

 there are few data available on Western North 

 Atlantic populations. The worldwide, pre- 

 exploitation population level is estimated at 300,000 

 animals. Current population estimates for the 

 North Atlantic range between 100 and 555 

 individuals. (NMFS, 1991). 



2. Non-Endanpered Cetaceans 



Minke whales (Balaenoptera acutorostrata : 15 to 30 

 feet, or 4.6 to 9.1 meters in length) are the smallest 

 of the balaenopterid species of cetaceans. Although 

 rehable population figures for the Western North 

 Atlantic stock are not known, minke whales are 

 commonly seen in the northern Stellwagen Bank 



and southern Jeffreys Ledge area from March until 

 November. The species may also overwinter in 

 these areas; although further winter surveys would 

 be necessary to make this determination. 



Minke whale abundance in the study area is 

 highest in the spring and the late summer/early fall. 

 Larger concentrations of muikes appear during the 

 latter period, frequently observed in the immediate 

 vicinity of fin whales. It is likely that the seasonal 

 movements of this species are similar to those of fin 

 whales. 



Minkes feed primarily on schooling fish and 

 euphausiids, in particular herring, sand eel, capelin, 

 cod, pollack, mackerel, squid and copepods. 

 Although surface feeding patterns have been 

 documented, minkes more normally feed below the 

 surface. Calves are not generally seen in these 

 feeding areas. Due to their inconspicuous 

 appearance and behavior, population counts have 

 been difficult to obtain. 



Pilot whales (Globicephala spp .; 10 to 20 feet, or 

 3.0 to 6.1 meters in length) are distinguished by the 

 species' large bulbous head. The most common 

 species occurring in the Gulf of Maine is 

 Globicephala melaena . though in the Western North 

 Atlantic, this species is found in the same areas as 

 short-finned pilot whales (Globicephala 

 macrorhvncha '). These small jet black whales are 

 generally observed along the shelf edge in the 

 company of bottlenose dolphins (1(K) to 1,(K)0 meter 

 contour), but may also be seen in central and 

 northern Georges Bank/Great South Channel/ Gulf 

 of Maine areas between May and October. 



Pilot whales feed almost exclusively on squid 

 (Illex spp .). with fish and invertebrates as alternative 

 prey. Average pod size is approximately 20 animals. 



Orca (or killer) whales (Orcinus orcus; 22 to 30 

 feet, or 6.7 to 9.1 meters in length) are most 

 commonly seen in the southwestern Gulf of Maine 

 from mid-July to September, although these whales 

 are also known to overwinter in the Gulf of Maine. 

 Orcas have been frequently recorded on Jeffreys 

 Ledge, between the Isles of Shoals and on 

 Stellwagen Bank, where they are thought to follow 

 schools of bluefin tuna. As opportunistic feeders, 



