NMFS Biological Opinion on U.S. Navy training ... - Govsupport.us

FINAL PROGRAMMATIC BIOLOGICAL OPINION ON U.S. NAVY ACTIVITIES IN THE HAWAII RANGE COMPLEX 2008-2013
winter. In the summer month, they have been observed in Davis Strait (Mansfield 1985), the Gulf of St. Lawrence
(from the north shore of the St. Lawrence River estuary to the Strait of Belle Isle), and off eastern Nova Scotia
(Sears et al. 1987). In the eastern north Atlantic Ocean, blue whales have been observed off the Azores Islands,
although Reiner et al. (1993) do not consider them common in that area.
In 1992, the U.S. Navy conducted an extensive acoustic survey of the North Atlantic using the Integrated
Underwater Surveillance System’s fixed acoustic array system (Clark 1995). Concentrations of blue whale sounds
were detected in the Grand Banks off Newfoundland and west of the British Isles. In the lower latitudes, one blue
whale was tracked acoustically for 43 days, during which time the animal traveled 1400 nautical miles around the
western North Atlantic from waters northeast of Bermuda to the southwest and west of Bermuda (Gagnon and Clark
1993).
In the North Pacific Ocean, blue whales have been recorded off the island of Oahu in the main Hawai’ian Islands
and off Midway Island in the western edge of the Hawai’ian Archipelago (Barlow et al. 1994b; Northrop et al. 1971;
Thompson and Friedl 1982), although blue whales are rarely sighted in Hawai’ian waters and have not been reported
to strand in the Hawai’ian Islands. Nishiwaki (1966) reported that blue whales occur in the Aleutian Islands and in
the Gulf of Alaska. Although blue whales have not been observed off Alaska since 1987 (Leatherwood et al. 1982;
Stewart et al. 1987; Forney and Brownell 1996). No distributional information exists for the western region of the
North Pacific.
In the eastern tropical Pacific Ocean, the Costa Rica Dome appears to be important for blue whales based on the high
density of prey (euphausiids) available in the Dome and the number of blue whales that appear to reside there (Reilly
and Thayer 1990). Blue whales have been sighted in the Dome area in every season of the year, although their
numbers appear to be highest from June through November.
Blue whales have also been reported year-round in the northern Indian Ocean, with sightings in the Gulf of Aden,
Persian Gulf, Arabian Sea, and across the Bay of Bengal to Burma and the Strait of Malacca (Mizroch et al. 1984).
The migratory movements of these whales are unknown.
Historical catch records suggest that “true” blue whales and “pygmy” blue whale (B. m. brevicada) may be
geographically ddistinct (Brownell and Donaghue 1994, Kato et al. 1995). The distribution of the “pygmy” blue
whale is north of the Antarctic Convergence, while that of the “true” blue whale is south of the Convergence in the
austral summer (Kato et al. 1995). “True” blue whales occur mainly in the higher latitudes, where their distribution
in mid-summer overlaps with that of the minke whale (Balaenoptera acutorostrata). During austral summers, “true”
blue whales are found close to edge of Antarctic ice (south of 58° S) with concentrations between 60°-80° E and
66°-70° S (Kasamatsu et al. 1996).
Population Structure
For this and all subsequent species, the term “population” refers to groups of individuals whose patterns of increase
or decrease in abundance over time are determined by internal dynamics (births resulting from sexual interactions
between individuals in the group and deaths of those individuals) rather than external dynamics (immigration or
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