Eubalaena japonica
Creators: name: Russell A. Mittermeier
name: Don E. Wilson
Publisher: name: Lynx Edicions
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Mammalia
Cetacea
Balaenidae
Eubalaena
Eubalaena japonica

description: 2.
North Pacific Right Whale
Eubalaena japonica
French: Baleine du Japon / German: Pazifik-Nordkaper / Spanish: Ballena franca del Pacifico
Other common names: Japanese Whale, North-west Whale, Pacific Right Whale
Taxonomy. Balaena japonica Lacépède, 1818,
“du Japon” (=Japan).
This species is monotypic.
Distribution. Cold-temperate waters of the N Pacific, from Bonin Is (27° N, 142° E) and Ryukyu Is N to Yellow Sea, Sea ofJapan, Sea of Okhotsk, Bering Sea and Gulf of Alaska; occasionally reaching tip of Baja California, Mexico, to the S of E Pacific in winter. Except on their N summer grounds, only a few sightings in the E Pacific Ocean during the past 50 years.
Descriptive notes. Total length can exceed 1700 cm; weight exceeding ¢.80,000 kg. The North Pacific Right Whale is sexually dimorphic, with females growing slightly larger than males. It can grow somewhat larger but is similar to the North Atlantic Right Whale (E. glacialis) in external morphology and color. The North Pacific Right Whale is mostly black. Often,it has a small white area ventrally at the navel. In some individuals, this white coloration may form a much larger patch and may even extend laterally onto sides of the body. Some individuals are completely black. As with the North Atlantic Right Whale, the North Pacific Right Whale is stout and stocky. Maximum girth is approximately 75% of total body length, with its large head one-third of body length. Blowhole openings are widely separated and angle slightly to the sides. Spout is V-shaped and can reach up to 5 m. Rostrum is narrow, elongate, and arched. Approximately 200-270 thin baleen plates, each ¢.300 cm long, hang from each side of upperjaw. Baleen is gray-brown to black and is fringed with long, fine, grayish bristles. Eyes are located above apex of mouth. Patterns of callosities vary among individuals, but they are distributed in generally consistent locations, including behind blowhole, along rostrum, above eyes, along mandibles, and on chin. Hair may grow from areas with callosities. Callosities are naturally gray or black in color and are inhabited by cyamids. There is no dorsal fin or ridge on the wide, smooth back. Flippers are relatively large, broad, and paddle-shaped, with angular leading edges. There is a deep notch between wide, gently curving flukes.
Habitat. There is scant current information on habitat use of the North Pacific Right Whale. Historical records are indicative of pelagic feeding grounds in the Sea of Okhotsk, central and south-eastern Bering Sea, the Aleutian Islands, and Gulf of Alaska. In recent decades, consistent summer sightings of North Pacific Right Whales in the Sea of Okhotsk and off the Kuril Islands and Kamchatka coast substantiate these areas as important feeding grounds. Based upon repeated sightings west of Bristol Bay in the south-eastern Bering Sea, this region is important summer habitat. In this area, North Pacific Right Whales appear to select relatively shallow waters in the mid-continental shelf. Not surprisingly, distribution of North Pacific Right Whales has been noted to coincide with areas abundant in their primary prey, calanoid copepods. North Pacific Right Whales also appear to have an extensive pelagic distribution, and this is likely related to availability of adultstage copepods in these regions of the Pacific Ocean. Birthing grounds are not known. Areas that have been suggested as potential winter birthing grounds for the western North Pacific population, based on sightings and other information, include the Ryukyu Islands, Yellow Sea, Taiwan Strait, and Bonin Islands (= Ogasawara Islands). There is no information regarding the current wintering grounds of the eastern North Pacific population, except a sighting off southern Baja California, Mexico. In the central North Pacific, the southernmost recent sighting was off Maui, Hawaii. The possibility that the North Pacific Right Whale winters in distant, offshore regions has been raised.
Food and Feeding. North Pacific Right Whales are skim feeders. They appear to feed selectively on preferred prey species, as has been observed for the other balaenid species. Aggregations of North Pacific Right Whales feeding on copepods of the genus Neocalanus have been observed in the North Pacific Ocean, and these, along with copepods of the genus Calanus, are the main prey items reported for western North Pacific Right Whales. Stomachs of North Pacific Right Whales killed by Japanese and Soviet whaling vessels in the 1950s contained calanoid copepods (Neocalanus, Calanus, and Metnidia). Quantities of the amphipod crustacean Parathemisto japonica and the krill species Euphausia pacifica also were found in stomach contents. Scientists onboard the whaling vessels also conducted pelagic zooplankton sampling in areas of the southeastern Bering Sea occupied by whales and noted that Calanus finmarchicus (now recognized as C. marshallae) was abundant; the copepod was postulated to be important to North Pacific Right Whales in that region. More recently, North Pacific Right Whales have been observed feeding in shallow waters over the middle Bering Sea shelf where C. marshallae was the primary species in plankton samples.
Breeding. There is very little information on reproduction of the North Pacific Right Whale. Adult females can be mature as small as 1250 cm long. Based on data from fetuses of two pregnant females killed by Soviet whaling vessels, S. K. Klumov in 1962 gave a very preliminary estimate that mating may occur in November-December. He calculated gestation of the North Pacific Right Whale at c¢.11-12 months, butthis estimate is too short given gestation of other cetaceans and based on gestation of Southern Right Whales (E. australis) estimated at 12-13 months.
Activity patterns. Similarly to their congeners, North Pacific Right Whales are slow moving. They were noted to remain calm and generally show no attempt at avoidance when approached by whaling vessels. Although North Pacific Right Whales were reported by soviet scientists to make shore dives of 4-6 minutes with maximum dive times of nine minutes,it is likely that most feeding dives for this species average 10-20 minutes like those of their congeners, the North Atlantic Right Whale and the Southern Righ Whale.
Movements, Home range and Social organization. The North Pacific Right Whale appears to make northward migrations to high latitudes in spring and southward to lower latitudes in autumn. They may occupy both offshore and inshore areas in the Sea of Okhotsk, Bering Sea, and Gulf of Alaska as their primary summer feeding grounds. There have been repeated sightings in the south-eastern Bering Sea west of Bristol Bay and off the south side of Kodiak Island. Wintering grounds of North Pacific Right Whales are not well known, and only scattered records ofsingle individuals exist.
Status and Conservation. CITES Appendix I. Classified as Endangered on The IUCN Red Last, with the north-eastern North Pacific subpopulation classified as Critically Endangered. The original distribution of the North Pacific Right Whale was never documented in any detail before it was depleted by the middle of the 19" century. Today, whales are found in winter around the Bonin Islands, Ryukyu Islands, and Yellow Sea (west of the Korean Peninsula); in summer (feeding grounds), they are found from the Sea of Okhotsk and Kuril Islands, north to off the Kamchatka Peninsula, Commander Islands, and the western Bering Sea. In the East Pacific Ocean, North Pacific Right Whales moved north off the California coast and along the western coast of North America, but since the 1990s, they have only been seen regularly from summer to early autumn in the south-eastern Bering Sea, west of Bristol Bay, Alaska (¢.57°-59° N), and sometimes in the Gulf of Alaska. Western and eastern populations of the North Pacific Right Whale have different geographic distributions, population sizes, and stranding histories. In the western North Pacific Ocean, they are poorly known, and the only available population estimate is outdated and only preliminary based on data collected during dedicated line-transect surveys for Common Minke Whales (Balaenoptera acutorostrata), conducted in the Sea of Okhotsk during 1989, 1990, and 1992. The resulting population estimate of 922 North Pacific Right Whales was based on only a limited number of sightings and the confidence interval was wide (404-2108 individuals). However, the most recent [UCN assessment gives 400 for the Sea of Okhotsk population size. Sighting data are available from additional Russian and Japanese surveys conducted since 1992, but they have not yet been analyzed. No assessment has been made for the north-western subpopulation of the North Pacific Right Whale because of the outdated population estimate. No estimate is available for the pre-whaling size of this subpopulation, but large numbers of right whales were taken in the North Pacific during the 19" century, and illegal Soviet pelagic catches made during the 1960s included at least 152 whales taken from the Sea of Okhotsk. Major current threats are bycatch in various types of fishing gear. No deaths of North Pacific Right Whales from ship strikes have been reported, butthis is likely an important threat because of their coastal nature in much of their distribution, especially in coastal waters of China, Korea, and Japan. In the Sea of Okhotsk, future oil and gas activities will pose risks to North Pacific Right Whales on their summer feeding grounds. The current abundance estimate for the north-eastern North Pacific population is only ¢.30 individuals, based on independent photo-identifications and genetic mark-recaptures. No pre-whaling estimate is available for this population. They were depleted quickly in the middle of the 19" century. Some were also killed during the start of modern commercial whaling off Alaska and British Columbia, Canada,in the early part of the 20" century and then after c.30 years of no catches,illegal Soviet pelagic whaling operations killed a minimum of 529 individuals in the Gulf of Alaska and south-eastern Bering Sea in the 1960s. Bycatch in various types of fishing gear and ship strikes are the two most important current threats, but to date, there have not been any confirmed deaths. Potential future threats include oil and gas activities on summer feeding grounds of the North Pacific Right Whale.
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description: Published as part of Russell A. Mittermeier & Don E. Wilson, 2014, Balaenidae, pp. 186-215 in Handbook of the Mammals of the World – Volume 4 Sea Mammals, Barcelona :Lynx Edicions on pages 210-211, DOI: 10.5281/zenodo.6595811