North Pacific right whale (Eubalaena japonica) COSEWIC assessment and status report: chapter 6
Biology
Basic aspects of the biology and ecology of the North Pacific right whale remain poorly understood.
Reproduction
The location of breeding and the calving grounds is unknown (Brownell et al. 2001). Nothing is known about reproduction, longevity, age at sexual maturity, or sex ratio, but reproductive rates are likely to be low based upon information from other right whale species.
Until a sighting of a cow and calf in the Bering Sea on August 24, 2002 (LeDuc 2004) there had been no confirmed sightings of calves in the eastern North Pacific since at least 1900 (Brownell et al. 2001). Two or three cow-calf pairs were observed in the southeastern Bering Sea during the summer of 2004 (Robert Pitman, Southwest Fisheries Center, NMFS, personal communication).
Survival
There are no reliable estimates of survival for the eastern North Pacific right whale.
Physiology
Virtually nothing is known about the physiology of eastern North Pacific right whales.
Movements/dispersal
Migratory patterns of the North Pacific right whale are unknown, although in other oceans right whales generally spend the summer on high-latitude feeding grounds and migrate to more temperate waters during the winter (Braham and Rice 1984). Historically, North Pacific right whales were found across a wide range of latitudes during both summer and winter, which is evidence of a staggered or diffuse migration (Scarff 1991). This seasonal movement is also evident in monthly plots of 20th century and historical records (Clapham et al. 2004).
Nutrition and interspecific interactions
North Pacific right whales are low trophic level filter feeders. They feed entirely on zooplankton, primarily copepods (Calanus spp.) (Omura et al. 1969). A single whale can eat several metric tons of copepods a day. It is the right whales’ dependence on large, dense aggregations of prey that determines much of their distribution.
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