Bowhead whales (Balaena mysticetus) were seen in autumn 1992 and 1993
only along the northern coast of Chukotka, Russia, although an extensi
ve area of the Chukchi Sea was searched during ship cruises. Single-da
y counts of 76 and 50 bowheads were made on 1 October 1992 and 3 Octob
er 1993, respectively, with only a few whales seen on other days. Whal
es seen between Cape Schmidt and Cape Vankarem on 1 October 1992 appea
red to be feeding, but there was no means to detect or sample subsurfa
ce forage that year. On 3 October 1993, bowheads appeared to be feedin
g in an area where a 5 m x 8 km patch of zooplankton was identified, v
ia acoustics, at 25-30 m in water 35 m deep. A vertical-tow sample nea
r the patch indicated the euphausiid Thysanoessa rachii, a common bowh
ead prey species, was abundant in the water column. The location of th
e zooplankton patch corresponded with a sharp salinity (proxy density)
gradient. In addition, whale distribution coincided with a surface th
ermal boundary, identified by satellite-borne Advanced Very High Resol
ution Radiometer (AVHRR) imagery. The confinement of bowhead sightings
to the northern coast of Chukotka in 1992-93 corresponds to reports f
rom autumn surveys in 1979, 1980 and 1990, while the association of wh
ales with physical oceanographic fronts is similar to findings from a
study of bowhead feeding areas in the southern Beaufort Sea. These obs
ervations suggest that the Chukotka coast may be an important feeding
or staging area for the Bering Sea stock and that oceanographic patter
ns influencing whale occurrence may be identifiable from standard ocea
nographic measurements.