Endangered whales Species and PopulationsWe would like to explain about endangered whales with the example being the blue whale. The blue whales are listed as an endangered whales under the IUCN Red List 2008 and the U.S. Endangered Species Act 2007, as depleted under the Marine Mammal Protection Act 31/12/2007 and is listed in Appendix I of CITES (see below what the categories mean). There are several reasons why blue whales are threatened. The hunting of the blue whale already began in the late 1800's and peaked between the early 1900's and 1940. During the 1930/31 season almost 30000 blue whales were killed. The number of Antarctic blue whales decreased from about 350000 animals before whaling began to approx. 460 afterwards. Another 11000 blue whales were taken in the North Atlantic and 9500 in the North Pacific during the first half of the 20th century. Only the worldwide protection of blue whales in 1966 stopped this slaughtering. Today there are between 600 and 1500 blue whales in the North Atlantic , 3000-4000 in the North Pacific and 1000-2000 in the Antarctic waters. The Antarctic blue whale is listed as a critically endangered subspecies. Since blue whales get sexually mature with an age of usually 8 to 10 years and give birth only every two or three years to one single calf, it would take 2-3 centuries until the populations have recovered although there may be some increase in pregnancy rate and a decrease in the mean age of maturity which is often the case in depleted whale and dolphin populations. These mechanisms are limited by gestation and suckling period.
Additionally minke whales and blue whales seem to prefer different habitats since minke whales are most common within the pack ice where they are not accessible to whalers. So probably more minke whales than blue whales escaped the hunting and therefore minke whale population sizes have never decreased as much as those of blue whales. Additionally there are still threats today. At least 25% of the blue whales identified in the St. Lawrence (East Canada) carry scars from ship collisions. There are also persistent contaminants accumulating in the whales over time which could have an impact on reproduction of these animals. Another current problem which may have a negative influence on the recovery of the blue whales worldwide is noise pollution. Noise levels in the oceans have dramatically increased during the last decades and include frequencies which are used by the blue whales to communicate over huge distances. There are many other endangered whale species threatened today. This is shown by several lists which conclude the current status of whale and dolphin (and other) species and populations. When such a list is established usually at least the following criteria are considered: number of animals in the population (population size)extend of human influence on the population/speciescondition of the habitat which is used by the population/speciestrade possibilities for products from the population/species.
Endangered Whale TableThe following table shows which whale and dolphin species are CR = critically endangered, EN = endangered, VU = vulnerable, DD = data deficient or nt = near threatened under the IUCN (World Conservation Union) Red List 2008 and/or E =endangered under the U.S. Endangered Species Act and/or D = depleted under the Marine Mammal Protection Act 31/12/2007 and /or listed in I = Appendix I or II = Appendix II of CITES, 01/07/08. Critically endangered under the IUCN Red List means: threatened and in danger of extinction Endangered under the U.S. Endangered Species Act means: any species which is in danger of extinction throughout all or a significant portion of its range. Species listed in Appendix I of CITES are are threatened with extinction. CITES prohibits international trade with any products of them except for non-commercial purposes e.g. scientific research.
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One theory about the still little number of blue whales in Antarctica is that minke whales have recovered to a level which makes them food competitors and therefore slows down the increase of Antarctic blue whales. On the other hand the very slow recovery and listing of blue whales as being endangered whales, can be explained completely by massive illegal hunting of these animals carried out by the former Soviet Union which lasted until 1972. During 1964 and 1972 another 852 Antarctic blue whales were killed although this subspecies was already in danger of extinction. Between 1951 and 1972 falsification of data took place since catch was continuously underreported.