Eubalaena japonica

North Pacific right whale

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North Pacific right whale North Pacific right whale

 

Description

The right whales have been driven nearly to extinction as the species preferred by commercial whalers and have been hunted in spite of international bans.  There are perhaps several hundred in the western Pacific, and perhaps only a handful in the eastern Pacific.  Between 1960 and 1996, only a few solitary animals were sighted; in 1996, a group of four was found in the Bering Sea.

These animals are among the largest mammals and can weigh as much as 100 tons at maturity.  They can live 70 years or longer. The North Atlantic right whale differs in skin color from the North Pacific right whale and the cold waters of the Arctic Circle are a natural impediment to the mingling of these two groups.

Geography

Prior to the onset of commercial whaling in the 1830s, right whales were widely distributed across the North Pacific (Scarff 1986, Clapham et al. 2004, Shelden et al. 2005). In the eastern North Pacific, the waters adjacent to the Aleutian Islands and much of the Bering Sea below 60oN were major feeding grounds during spring, summer and autumn, as was virtually the entire Gulf of Alaska. Neither the historical nor the present-day breeding/calving grounds for this subpopulation have been identified.


In recent decades, both the southeastern Bering Sea and the western Gulf of Alaska (shelf and slope waters south of Kodiak) have been the focus of sightings as well as illegal Soviet catches (see below). Recent acoustic detections of right whale calls have been made in both areas using autonomous recording packages deployed for extended periods (Moore et al. 2006). They confirm the presence of right whales in the southeastern Bering Sea from May into November; records from the Gulf of Alaska are somewhat more sporadic, but include detections in August and September.

 

Seasonal movements are evident in sighting and catch data from the 20th century, with a general northward migration into the Gulf of Alaska and Bering Sea in spring and summer, and a gradual movement away from these areas in autumn (Clapham et al. 2004, Shelden et al. 2005). There are very few records of right whales anywhere in the North Pacific in winter.

 


In general, the majority of eastern North Pacific right whale sightings (historically and in recent times) have occurred from about 40º N to 60º N. There are historical records from north of 60º N, but these are rare and many are likely to be misidentified bowhead whales. Right whales have on rare occasions been recorded off California and Mexico, as well as off Hawaii. However, as noted by Brownell et al. (2001), there is no evidence that either Hawaii or the west coast of North America from WashingtonState to Baja California has ever been important habitat for right whales. Consequently, the few records from this region are considered to represent vagrants.

 

Recent data indicate that while the present range of the remnant eastern subpopulation is likely reduced relative to pre-whaling times, the southeastern Bering Sea and western Gulf of Alaska (south of Kodiak) remain important habitats.

 

Ecosystem

Little is known about habitat use by eastern North Pacific right whales. The rarity of coastal records in winter in either historical or recent times suggests that their breeding grounds may have been offshore (Clapham et al. 2004). This is in contrast to southern and North Atlantic right whales, both of which form inshore breeding concentrations. There is clearly some northward migration in summer and southward in winter (Clapham et al. 2004), but the location of the wintering grounds is unknown. The historical catches show that in summer the population occurred mainly on feeding grounds in the Bering Sea and Gulf of Alaska. Data on food habits are sparse, but suggest that right whales in the eastern North Pacific feed primarily on copepods of the genera Calanus and Neocalanus (Shelden et al. 2005). Primary habitats today include core areas of the southeastern Bering Sea and an area off eastern Kodiak Island, which were also significant parts of the range in the past.

Conservation

North Pacific right whales are currently one of the rarest whale species, with some estimates placing the world population at around 1400 individuals and other estimates substantially smaller (~500 in the western Pacific and numbering less than 100 in the eastern Pacific). They were previously common in the north Pacific but were relentlessly pursued by whalers throughout the 19th century. Japanese whaling of this species began in the late 1500's and whaling by Americans and Europeans began in the 1800's. As many as 37,000 north Pacific right whales were killed in a 70 year period from 1839 to 1909, leaving populations at a fraction of their previous levels. Right whales became protected by international agreement in 1935 and by law in 1946 by the International Whaling Commission. Illegal hunting continued through the 1960's, during which time Soviet whaling ships took almost the entire remaining population of eastern Pacific right whales (372 individuals), leaving the population at an estimated 50 individuals. The eastern Pacific population is considered critically endangered and populations in the western Pacific are considered endangered by the IUCN. These whales have been protected from hunting since 1970, but entanglements and deaths continue to occur occasionally. Only 1,965 north Pacific right whales were observed in the 20th century.

Appointed in 1987, The Northern Right Whale Recovery Team created a recovery plan for both north Pacific and north Atlantic right whales. The National Marine Fisheries Service approved the recovery plan in 1991, which strives to see both species fully recover but first focuses on recovery to bring their status from “endangered” to merely “threatened”. Some actions recommended in the recovery plan include eliminating injury caused by ship collision, fisheries, and fishing gear; monitoring population size and trends; maximizing efforts to free entangled or stranded right whales; obtaining scientific information from dead specimens; and protecting habitats that are essential for right whales to survive.

US Federal List: endangered

CITES: appendix i

IUCN Red List of Threatened Species: critically endangered

 

Threats

ommercial hunting for right whales in the eastern North Pacific was initiated by Europeans and Americans in the 1830s; by about 1900, the subpopulation had been reduced to a fraction of its original abundance, as evidenced by the comparatively low number of 20th century sightings (Brownell et al. 2001). Although legally protected by the IWC since 1946 (and by an earlier agreement in 1935), illegal hunting continued into the 1960s with the Soviet catches of 372 animals in the eastern North Pacific (Doroshenko 2000, Brownell et al. 2001).

There is currently no evidence of human-related mortality or injury, but the very low observer effort and remoteness of the right whale’s habitats probably means that most deaths and injuries pass unrecorded.

The eastern North Pacific subpopulation is subject to anthropogenic threats such as entanglements in fishing gear, disturbance by vessels and other noise, collisions, and possibly petroleum-related and other contaminants.

As compared with the intensively studied North Atlantic right whale, the more offshore and remote distribution of eastern North Pacific right whales may be an advantage in terms of less intensive exposure to human impacts, but the disadvantage is that impacts that do occur are less likely to be detected and their consequences are harder to ascertain and evaluate.

Small populations numbering less than a few hundred individuals can have a number of interacting effects that accelerate overall risk (Gilpin and Soule, 1986). Among those effects are demographic stochasticity, inbreeding depression and density depensation (Allee effects). Although direct data are lacking for marine mammals at low density, the expectation is that these threats could be serious because cetaceans are social animals with low reproductive output. 

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