Eubalaena glacialis

Дата канвертавання24.04.2016
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Four species of whales are catagorised as endangered on the IUCN Red List all having been depleted by commercial whaling. The northern right whale Eubalaena glacialis is the most endangered of the large whales with an estimated population of under a 1,000. Protected from hunting the most serious threat is now from vessel collision and entanglement in fishing nets. Recent estimates put the number of blue whales Balaenoptera musculus at between 400-1,400 in the Southern Hemisphere (this subpopulation is classed as endangered) and possibly approaching 4,000 in the North Atlantic (a vulnerable stock) and North Pacific (at a lower risk of extinction). Fin whales Balaenoptera physalus are thought to number about 40,000 in the Northern Hemisphere and only about 15-20,000 in the Southern Hemisphere, a small percentage of the original population levels. There are no reliable estimates of the number of sei whales Balaenoptera borealis although its patchily distributed populations are well below pre-exploitation levels.
There has been some evidence of recovery in three species including the humpback whale Megaptera novaeangliae. The most intensively studied of all whale species, its coastal habits made it susceptible to shore based whaling in the past and now damage from shipping, pollution and entanglement in nets. The economic value of humpbacks to the whale-watching industry is increasing the support for protection measures but with the possible depletion of food supplies by fisheries, particularly the krill fisheries of the Southern Ocean, the vulnerable status of approximately 20,000 remaining animals is far from being improved. The southern right whale Eubalaena australis was regarded as vulnerable in 1991 but is now classed as at lower risk with dependence on conservation measures. There is evidence that at least two populations (with nursery areas off Argentina and South Africa) are beginning to recover and total population estimates are about 1,500-4,000. The bowhead whale Balaena mysticetus was classed as endangered in 1988 but has also been raised to a lower risk (conservation dependent) category overall with a total population of over 7,000. The two subpopulations of Baffin Bay and Okhotsk Sea are, however, still endangered with the stock in the Svalbard-Barents Sea critically endangered. They are heavily protected by the International Whaling Commission (IWC) with the Alaskan Eskimos being allowed a regulated catch each year. The biggest threats are more likely to come from the industrial activity in the Arctic such as oil and gas exploration and global warming the effects of both being difficult to define and evaluate.

Of the three populations of gray whales Eschrichtius robustus the North Atlantic one is extinct but two stocks in the Pacific still survive and are thought to number around 22,000. They are at a lower risk but still dependent on protective measures set up by the IWC limiting hunting to the aboriginal communities in Russia. They are shallow water feeders and are vulnerable to human disturbance and entanglement in fishing nets.

There are still several species where the numbers are insufficiently known such as the Bryde's whale Balaenoptera edeni found in tropical and subtropical seas. A rough population estimate puts numbers at 40-80,000 but the threat of illegal hunting and depletion of food supplies in many areas may make this figure too high.
Considerable uncertainty exists as to the number of sperm whales Physeter catodon alive today. They may still be fairly numerous but the selective killing of the larger breeding age males over many years has upset the male-to-female ratio causing a decline in the birth rate in some populations. Sperm whales have been classified as vulnerable as there may be as few as 500,000.
The white whale or beluga Delphinapterus leucas found in the Arctic and Subarctic regions is thought to total about 100,000 and is made up of several small populations. The smaller ones such as stocks from the St Lawrence River and Cook Inlet, 1,238 and 347 respectively, are particularly vulnerable to hunting or habitat deterioration. So although the total numbers are quite high depletion of the individual populations are giving cause for concern. Harvesting of the larger populations, such as the 17,675 belugas found in the East Bering Sea, is still being carried out by aboriginal communities but threats from other human activities are putting this subsistence harvesting at risk. The increase in oil and gas exploration in the Arctic in recent years has increased the shipping traffic as well as urban and industrial pollution. The primary incidental catch is from interaction with fishing nets and overfishing is thought to be reducing the animals’ food supplies. Less is known about a close relative of the beluga, the narwhal Monodon monoceros. Rough estimates of the stock in Baffin Bay, which is heavily exploited in Greenland and Canada, was recently estimated at 34,000 animals and the Hudson Bay stock at about 1300. This species is also threatened by continued subsistence harvesting combined with similar human activities to those faced by the beluga.
Little is known of the status of the beaked whales except both Arnoux's beaked whale Berardius arnuxii and Baird's beaked whale Berardius bairdii as well as the northern (Hyperoodon ampullatus) and southern (Hyperoodon planifrons) bottlenose whales are thought to be at lower risk with dependence on conservation measures. Of these four species the northern bottlenose whale was the only one significantly depleted by whaling. The cessation of whaling by the primary nation Norway in 1973 has led to an improvement in the vulnerable status it had in 1988.

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