Balaena mysticetus (Okhotsk Sea subpopulation)
|Scientific Name:||Balaena mysticetus (Okhotsk Sea subpopulation)|
|Taxonomic Notes:||The Okhotsk Sea Bowhead is a subpopulation of Balaena mysticetus Linnaeus, 1758. See also global assessment for the Bowhead Whale. Genetic analyses have confirmed that the Okhotsk Sea Bowheads are distinct from the Bering-Chukchi-Beaufort Sea Bowheads and are a separate, isolated subpopulation (LeDuc et al. 2005).|
|Red List Category & Criteria:||Endangered D ver 3.1|
|Assessor(s):||Cooke, J.G., Brownell Jr., R.L. & Shpak, O.V.|
|Reviewer(s):||Clapham, P.J., Reeves, R. & Taylor, B.L.|
The Okhotsk Sea subpopulation of Bowhead Whales probably contains fewer than 250 mature individuals and therefore qualifies for Endangered under criterion D. Recent evidence suggests an ongoing decline. If the decline is confirmed and quantified, the subpopulation could be reclassified as Critically Endangered under criterion C1.
|Previously published Red List assessments:|
|Range Description:||Bowhead Whales are found in the northern and western Sea of Okhotsk from Nikolaya Bay to Udskaya Bay (Shantar region) in the west, the Kashevarova Bank (south of Iona Island) and east to Shelikhova Bay, including Gizhiginskaya and Penzhinskaya Bays (Berzin and Doroshenko 1981, Ivashchenko and Clapham 2010, Meschersky et al. 2014, Shpak 2016). Doroshenko (2000) suggested that the Bowhead Whales probably winter on the Kashevarova Bank in patches of open water within the main sea ice zone, then follow the melting ice to Shelikova Bay (northern Okhotsk Sea) in spring, thence to the Shantar region (western Okhotsk Sea) in summer where the ice persists longest. The lack of Bowhead sightings on any of the Japanese-Russian systematic surveys of cetaceans in the Okhotsk Sea conducted in 1989, 1990, 1998, 1999, 2000 and 2003 confirms that animals from this subpopulation are rarely found in the offshore Okhotsk Sea in summer (Ivashchenko and Clapham 2010).|
|FAO Marine Fishing Areas:|
Pacific – northwest
|Range Map:||Click here to open the map viewer and explore range.|
Bowhead Whales have been seen regularly during Russian surveys in the northeastern and western Sea of Okhotsk. Berzin et al. (1991) reported sightings every year from 1982 through 1990, except 1985, with up to 72 whales apparently seen on one day. Ivashchenko and Clapham (2010) tabulated records of Bowhead Whale sightings in the Okhotsk Sea from 1965 to 2004, but were unable to quantify the associated survey effort. Berzin et al. (1990) believed the individuals in the western Okhotsk Sea to number at least 250–300 animals, while Vladimirov (1994) considered that there were 300-400 Bowhead Whales in the entire Okhotsk Sea. These values appear to be based primarily on the numbers seen, without evaluation of effective search effort.
Genetic sampling was conducted on samples from the Shantar region, western Okhotsk Sea, during the summer months (July-September) in 1995, 1996, 1999, 2000 and 2011-2016 (LeDuc et al. 2005, Meschersky et al. 2014, Shpak et al. 2017). Applying an open-population genetic mark-recapture model to the 2011-2016 data, Shpak et al. (2017) estimated the total number of animals alive (not necessarily at one time) over the period at 388 ± 108 animals. An analysis of the full 1995-2016 dataset yielded a declining population trajectory reaching 218 living animals (coefficient of variation 0.22) by 2016 (Cooke et al. 2017,; IWC 2018a). The median estimated rate of decline was 5% per year but the decline was only borderline statistically significant. If there are individuals that do not enter the western Okhotsk Sea in summer, then the size of the entire Okhotsk Sea subpopulation would be larger. It is currently unclear whether the individuals seen in Shelikhova Bay (northern Okhotsk Sea) in spring and early summer are among the individuals seen in the Shantar region (western Okhotsk Sea) in summer and autumn (Meschersky et al. 2014). There is some evidence from whaling data that younger whales, and mothers with calves, predominated in Shantar while older whales were found in Shelikova Bay (Ivashchenko and Clapham 2010).
There are no specific data on the proportion of mature animals in this subpopulation, but Taylor et al. (2007) estimated the proportion mature for a Bowhead Whale population to be in the range 39%-65%, depending on population trend. The number of mature individuals in the Okhotsk Sea is, therefore, likely fewer than 250.
The historical information on catches is briefly reviewed by Ivashchenko and Clapham (2010). The subpopulation was subject to intensive commercial whaling by mainly American whalers during the short period 1848-1857 although sporadic catches continued until 1913 (Doroshenko 1996, 2000). Lindholm (1888) mentioned that during 1855-57, 438 whaling ships were operating in the Okhotsk Sea and took “no fewer than 6,654 whales” but these may not all have been Bowheads and the source of his information is not given. The Soviet whaling fleet Vladivostok illegally took 133 Bowhead Whales in the Shantar region in 1968 after the fleet Aleut had taken an unrecorded number, but at least 18, in 1967 (Doroshenko 2000).The pre-whaling abundance is uncertain, but was many times higher than the current level, based upon the number of whales caught in the mid-19th century. There are no direct data on generation time, but it is estimated to be 52 years by analogy with the Bering-Chukchi-Beaufort Sea subpopulation (Taylor et al. 2007). The first main reduction occurred over 156 years ago, and thus does not trigger the past reduction (A1) criterion for a Red List category. The take of at least 151 Bowhead Whales by Soviet whalers in 1967-68 will have caused a second, probably lesser reduction.
|Current Population Trend:||Decreasing|
|Habitat and Ecology:|
Little is known about the specific ecology of the Okhotsk Sea Bowhead Whale subpopulation, but small to medium-sized crustaceans, especially krill (euphausiids) and copepods, form the bulk of the Bowhead Whale diet in the Alaskan and Canadian Arctic (Lowry et al. 2004, Pomerleau et al. 2011). Samples of the water in Ulbansky Bay in 2013 contained abundant small copepods, mainly Oithona similis, in the areas where Bowhead Whales were feeding, and much lower densities of euphausiids (Melnikov and Fedorets 2016).
|Generation Length (years):||52|
The cause of the recent apparent population decline of Okhotsk Sea Bowheads, if real, is not understood. However, the apparent concentration of most or all of the subpopulation into a relatively limited area in summer may be a risk factor.
Currently this subpopulation is not subject to hunting, but faces other potential threats. Increasing fishing activity in the areas of Bowhead Whale concentration may become a concern. For example, a mother and calf were entangled in a salmon trap in Udskaya Bay in 2012: the calf died but the mother was released. Several cases have been reported of Bowhead Whales tearing through coastal salmon nets (Shpak and Paramonov 2018). Brownell (1999) reported that a Bowhead was taken in the crab pot fishery in the north central Okhotsk Sea in September 1995. There is a substantial crab fishery in the Okhotsk Sea, including in the Ayan-Shantar region where the most Bowheads occur. However, Shpak and Stimmelmayr (2017) found relatively few and mainly minor fishing gear scars on the Bowheads they examined. Thus, it is unclear whether fishing gear is a significant threat to Okhotsk Sea Bowheads at this time. Harassment by tour boats and others has also been observed. Expanding industrial and tourism activities in the area and plans for offshore oil extraction may have some impact on Bowhead Whales (Shpak and Paramonov 2018).
The Bowhead Whale is an ice-adapted species. The coastal Bowhead habitat in the western Okhotsk Sea is already ice-free in summer and autumn, and most climate models predict substantially reduced winter ice in the Okhotsk Sea during the 21st century (Arzel et al. 2006). It is unclear what effect the reduction of ice-cover will have on Bowhead Whales. Cases of predation by Killer Whales (Orcinus orca) have recently been observed (Shpak and Paramonov 2018), and a shorter ice-cover season may result in Bowheads being exposed to Killer Whale predation earlier in the season and for longer periods of time (IWC 2018b).
Bowhead Whales have been protected from commercial whaling by the International Convention for the Regulation of Whaling (ICRW) since its entry into force in 1948. The species, including this population, is protected under Russian law through its inclusion on the Red Book of the Russian Federation. The Bowhead Whale has been included in Appendix I of the Convention on International Trade in Endangered Species of Wild Flora and Fauna (CITES) Appendix I since 1975 and is listed in Appendix I of the Convention for the Conservation of Migratory Species (CMS).
|Citation:||Cooke, J.G., Brownell Jr., R.L. & Shpak, O.V. 2018. Balaena mysticetus (Okhotsk Sea subpopulation). The IUCN Red List of Threatened Species 2018: e.T2469A50345920.Downloaded on 22 September 2018.|
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