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
and Mitchell 1971; Cummings and Thompson 1971, 1977, 1994; Cummings and Fish 1972; Thompson et al. 1996;
Rivers 1997; Tyack and Clark 1997; Clark et al. 1998).
Blue whale moans within the low frequency range of 12.5-200 Hz, with pulse duration up to 36 seconds, have been
recorded off Chile (Cummings and Thompson 1971). A short, 390 Hz pulse also is produced during the moan. One
estimate of the overall source level was as high as 188 dB, with most energy in the 1/3-octave bands centered at 20,
25, and 31.5 Hz, and also included secondary components estimates near 50 and 63 Hz (Cummings and Thompson
1971).
As with other vocalizations produced by baleen whales, the function of blue whale vocalizations is unknown,
although there are numerous hypotheses (which include include: maintenance of inter-individual distance, species
and individual recognition, contextual information transmission, maintenance of social organization, location of
topographic features, and location of prey resources; see the review by Thompson et al. 1992 for more information
on these hypotheses). Responses to conspecific sounds have been demonstrated in a number of mysticetes, and there
is no reason to believe that fin whales do not communicate similarly (Edds-Walton 1997). The low-frequency sounds
produced by blue whales can, in theory, travel long distances, and it is possible that such long-distance
communication occurs (Payne and Webb 1971, Edds-Walton 1997). The long-range sounds may also be used for
echolocation in orientation or navigation (Tyack 1999).
Cetaceans have an auditory anatomy that follows the basic mammalian pattern, with some modifications to adapt to
the demands of hearing in the sea. The typical mammalian ear is divided into the outer ear, middle ear, and inner ear.
The outer ear is separated from the inner ear by the tympanic membrane, or eardrum. In terrestrial mammals, the
outer ear, eardrum, and middle ear function to transmit airborne sound to the inner ear, where the sound is detected
in a fluid. Since cetaceans already live in a fluid medium, they do not require this matching, and thus do not have an
air-filled external ear canal. The inner ear is where sound energy is converted into neural signals that are transmitted
to the central nervous system via the auditory nerve. Acoustic energy causes the basilar membrane in the cochlea to
vibrate. Sensory cells at different positions along the basilar membrane are excited by different frequencies of sound
(Tyack 1999). Baleen whales have inner ears that appear to be specialized for low-frequency hearing. In a study of
the morphology of the mysticete auditory apparatus, Ketten (1997) hypothesized that large mysticetes have acute
infrasonic hearing.
3.3.1 Fin whale
Distribution
Fin whales are distributed widely in every ocean except the Arctic Ocean. In the North Pacific Ocean, fin whales
occur in summer foraging areas in the Chukchi Sea, the Sea of Okhotsk, around the Aleutian Islands, and the Gulf of
Alaska; in the eastern Pacific, they occur south to California; in the western Pacific, they occur south to Japan. Fin
whales in the eastern Pacific winter from California south; in the western Pacific, they winter from the Sea of Japan,
the East China and Yellow Seas, and the Philippine Sea (Gambell 1985).
In the North Atlantic Ocean, fin whales occur in summer foraging areas from the coast of North America to the
Arctic, around Greenland, Iceland, northern Norway, Jan Meyers, Spitzbergen, and the Barents Sea. In the western
93