Marine Resources Assessment for the Marianas Operating ... - SPREP

AUGUST 2005 FINAL REPORT
widespread stock in the North Pacific and a smaller stock in the East China Sea (Donovan 1991).
There are no abundance estimates available for the fin whale in this area.
Habitat Preferences—The fin whale is found in continental shelf and oceanic waters (Gregr and
Trites 2001; Reeves et al. 2002). Globally, this species tends to be aggregated in locations where
populations of prey are most plentiful, irrespective of water depth, though those locations may shift
seasonally or annually (Payne et al. 1986, 1990; Kenney et al. 1997; Notarbartolo-di-Sciara et al.
2003). Fin whales in the North Pacific spend the summer feeding along the cold eastern boundary
currents (Perry et al. 1999). Littaye et al. (2004) determined that fin whale distribution in the
Mediterranean Sea was linked to frontal areas and upwelling, within large zooplankton patches.
Distribution—Fin whales are broadly distributed throughout the world’s oceans, usually in temperate
to polar latitudes, and less commonly in the tropics (Reeves et al. 2002). Fin whales are distributed
across the North Pacific during the summer (May through October) from the southern Chukchi Sea
(69°N) south to the Subarctic Boundary (approximately 42°N) and to 30°N in the California Current
(Mizroch et al. 1999). They have been observed during the summer in the central Bering Sea (Moore
et al. 2000). During the winter (November through April), fin whales are sparsely distributed from
60°N south to the northern edge of the tropics, near which it is assumed that mating and calving take
place (Mizroch et al. 1999). However, some fin whales have been sighted as far north as 60°N all
winter (Mizroch et al. 1999). Recoveries of marked whales demonstrate long migrations from lowlatitude
winter grounds to high-latitude summer grounds, and extensive longitudinal movements both
in-season and between years, within and between the main summer concentration areas (Mizroch et
al. 1999). There is also some evidence of a resident population of fin whales in the Gulf of California,
Mexico (Tershy et al. 1993). Such cases indicate that not all members of the species necessarily
make the long, north/south migrations that are typical of the species.
Information Specific to the Marianas MRA Study Area—There are no occurrence records for the
fin whale in the Marianas study area and vicinity, but this area is within the known distribution
range for this species. The endangered status of this large whale species was heeded when
determining its occurrence. There is a low or unknown occurrence of the fin whale seaward of the
50 m isobath. This takes in consideration the possibility of encountering this species in both
coastal and oceanic waters, knowing that fin whales can occur over the continental shelf and in
oceanic waters (Figure B-5). Occurrence patterns are expected to be the same throughout the
year.
Behavior and Life History—Fin whales feed by “gulping” (Pivorunas 1979). In the North Pacific, fin
whales appear to prefer krill and large copepods, followed by schooling fish such as herring, walleye
pollock, and capelin (Nemoto and Kawamura 1977). Single fin whales are most common. A fin whale
was sighted off Hawai’i in association with an adult humpback whale (Mobley et al. 1996), while a
group of 8 to 12 fin whales 400 km south of Hawai’i was in a mixed-species aggregation with dolphins
(Balcomb 1987).
Female fin whales in the North Pacific mature at 8 to 12 years of age (Boyd et al. 1999). Peak calving
is in October through January (Hain et al. 1992) after a gestation period of approximately 11 months.
Weaning may occur at 6 months (Boyd et al. 1999). The calving interval for fin whales ranges
between two to three years (Agler et al. 1993).
Fin whale dives are typically 5 to 15 min, separated by sequences of 4 to 5 blows at 10 to 20 sec
intervals (CETAP 1982; Stone et al. 1992; Lafortuna et al. 2003). Kopelman and Sadove (1995) found
significant differences in blow intervals, dive times, and blows per hour between surface-feeding and
non-surface-feeding fin whales. Croll et al. (2001) determined that fin whales dived to 97.9 m (+
standard deviation [S.D.] 32.59) with a duration of 6.3 (+S.D. 1.53) min when foraging and to 59.3 m
(+S.D. 29.67) with a duration of 4.2 (+S.D. 1.67) min when not foraging. Fin whale dives exceeding
150 m and coinciding with the diel migration of krill were reported by Panigada et al. (1999).
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