|Scientific Name:||Megaptera novaeangliae|
|Species Authority:||(Borowski, 1781)|
|Infra-specific Taxa Assessed:|
|Taxonomic Notes:||No subspecies are recognized. Phylogenetic analyses reveal that populations in different ocean basins do not represent distinct clades, but some maternal lineages can be traced back across hemispheric boundaries, indicating some level of inter-hemispheric gene flow, perhaps in the distant past (Baker et al. 1994).|
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor(s):||Reilly, S.B., Bannister, J.L., Best, P.B., Brown, M., Brownell Jr., R.L., Butterworth, D.S., Clapham, P.J., Cooke, J., Donovan, G.P., Urbán, J. & Zerbini, A.N.|
|Reviewer(s):||Taylor, B.L. & Notarbartolo di Sciara, G. (Cetacean Red List Authority)|
Although no final assessment of the current global population relative to its 1940 level is available, it seems, based on the recent rates of increase, unlikely that it is below the threshold (50% of the 1940 level) that would qualify the species for inclusion in the Vulnerable category under criterion A, The available population estimates total more than 60,000 animals, well above the C and D criteria thresholds for the Vulnerable category. The range of the humpback whale is not restricted, and therefore the species does not qualify for inclusion under Criterion B. The species is therefore listed as Least Concern. Completion of the ongoing Comprehensive Assessment by the IWC Scientific Committee will enable a more accurate determination of the level of recovery of the species.
The reasons for the change to Least Concern from the previous classification of Vulnerable (VU A1abd) are threefold:
(i) in the areas for which data are available, the population has continued to increase in the 10 years since the previous assessment;
(ii) abundance and trend data are available for more areas than were available for the previous assessment;
(iii) the criteria for Vulnerable have been changed: the threshold reduction for the A1 criterion has been changed from 20% to 50%.
Despite the encouraging global status, concern remains about apparently discrete and small subpopulations of humpback whales for which information about status is lacking. These include the Arabian Sea (isolated from the southern Indian Ocean), the western North Pacific, the west coast of Africa, and the South Pacific subpopulations in portions of Oceania (breeding stocks E and F) that likely feed in Antarctic Areas V and VI.
|Previously published Red List assessments:||
|Range Description:||The Humpback Whale is a cosmopolitan species found in all the major ocean basins (Clapham and Mead 1999), and all but one of the subpopulations (that of the Arabian Sea) migrate between mating and calving grounds in tropical waters, usually near continental coastlines or island groups, and productive colder waters in temperate and high latitudes.
Humpbacks in the North Atlantic range in summer from the Gulf of Maine in the west and Ireland in the east, and up to but not into the pack ice in the north; the northern extent of the humpback's range includes the Barents Sea, Greenland Sea and Davis Strait, but not the Canadian Arctic. They occur mainly in specific feeding areas, as noted below. In the winter the great majority of whales migrate to wintering grounds in the West Indies, and an apparently small number use breeding areas around the Cape Verde Islands.
In the North Pacific their summer range covers shelf waters from southern California, to the Gulf of Alaska, Bering Sea and southern Chukchi Sea, the Aleutian chain and Kamchatka, Kurile Islands, Okhotsk Sea and northeastern Japan. Wintering grounds are off the coasts of Mexico and Central America, around the Hawaiian Islands, the Bonin Islands, Ryukyu Islands and the northern Philippines, and possibly around additional island groups in the western North Pacific.
Humpbacks are abundant throughout the Antarctic in summer south to the ice edge, but not within the pack ice zone. In the winter, Southern Hemisphere whales aggregate into specific nearshore breeding areas in the Atlantic, Indian Ocean and Pacific, two of which extend north of the equator, i.e. off Colombia in the eastern Pacific and in the Bight of Benin in the Atlantic. Some wintering grounds are fairly localized, e.g. around island groups, and some are more diffuse, e.g. along the western coast of southern Africa and the southern coast of West Africa.
There is a resident year-round population in the Arabian Sea, which is genetically distinct from that of the southern Indian Ocean.
Humpbacks rarely enter the Mediterranean and are considered only visitors there (Reeves and Notarbartolo di Sciara 2006).
Native:American Samoa (American Samoa); Angola (Angola); Anguilla; Antigua and Barbuda; Argentina; Aruba; Australia; Bahamas; Bangladesh; Barbados; Benin; Bermuda; Bonaire, Sint Eustatius and Saba (Saba, Sint Eustatius); Brazil; Cameroon; Canada; Cape Verde; Cayman Islands; Chile; Cocos (Keeling) Islands; Colombia; Comoros; Congo; Congo, The Democratic Republic of the; Cook Islands; Costa Rica; Côte d'Ivoire; Cuba; Curaçao; Denmark; Djibouti; Dominica; Dominican Republic; Ecuador; El Salvador; Equatorial Guinea; Falkland Islands (Malvinas); Faroe Islands; Fiji; France; French Polynesia; French Southern Territories; Gabon; Gambia; Ghana; Greenland; Grenada; Guadeloupe; Guam; Guatemala; Haiti; Honduras; Iceland; India; Indonesia; Iran, Islamic Republic of; Ireland; Jamaica; Japan; Kenya; Kiribati; Korea, Democratic People's Republic of; Korea, Republic of; Madagascar; Malaysia; Maldives; Marshall Islands; Martinique; Mauritania; Mauritius; Mexico; Morocco; Mozambique; Myanmar; Namibia; Nauru; New Caledonia; New Zealand; Nicaragua; Nigeria; Niue; Northern Mariana Islands; Norway; Oman; Pakistan; Palau; Panama; Papua New Guinea; Peru; Philippines; Pitcairn; Portugal; Puerto Rico; Réunion; Russian Federation; Saint Helena, Ascension and Tristan da Cunha (Tristan da Cunha); Saint Kitts and Nevis; Saint Lucia; Saint Martin (French part); Saint Pierre and Miquelon; Saint Vincent and the Grenadines; Samoa; Sao Tomé and Principe; Senegal; Seychelles; Sint Maarten (Dutch part); Solomon Islands; Somalia; South Africa; South Georgia and the South Sandwich Islands; Spain; Sri Lanka; Taiwan, Province of China; Tanzania, United Republic of; Timor-Leste; Togo; Tonga; Trinidad and Tobago; Tunisia; Turks and Caicos Islands; Tuvalu; United Arab Emirates; United Kingdom; United States; Uruguay; Vanuatu; Venezuela, Bolivarian Republic of; Viet Nam; Virgin Islands, British; Virgin Islands, U.S.; Wallis and Futuna; Western Sahara; Yemen
|FAO Marine Fishing Areas:||
Arctic Sea; Atlantic – northeast; Atlantic – northwest; Atlantic – southeast; Atlantic – western central; Atlantic – eastern central; Atlantic – Antarctic; Atlantic – southwest; Indian Ocean – Antarctic; Indian Ocean – western; Indian Ocean – eastern; Pacific – southwest; Pacific – southeast; Pacific – northeast; Pacific – Antarctic; Pacific – northwest; Pacific – eastern central; Pacific – western central
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The Humpback Whale is better studied than other balaenopterid species, and migratory destinations are well known for some subpopulations.
A comprehensive assessment of North Atlantic Humpback Whales was completed by the IWC Scientific Committee in 2002, from which most of the information below is drawn (IWC 2002, 2003).
There is a distinct but relatively small winter aggregation in the east around the Cape Verde Islands – the site of fairly extensive 19th century Yankee whaling (Reeves et al. 2002). The major present-day North Atlantic breeding and calving area in the West Indies extends from Cuba in the west down the island chain as far as Venezuela; the largest breeding aggregations occur on Silver and Navidad Banks near the Dominican Republic, with much lower concentrations in Samana Bay (Dominican Republic), off the northwest coast of Puerto Rico, and around the Virgin Islands and the eastern Antilles. Some humpback whales have also been sighted in high-latitude waters during the winter, indicating that not all individuals migrate to the southern wintering grounds every year.
Six distinct feeding aggregations have been identified: Gulf of Maine, Gulf of St Lawrence, Newfoundland/Labrador, West Greenland, Iceland, North Norway (including Bear Island and Jan Mayen). Genetic and photo-identification data indicate that the six feeding aggregations represent relatively discrete subpopulations, fidelity to which is determined matrilineally. However, because whales from different feeding grounds all mix in a common breeding area in the West Indies, there is male-mediated nuclear gene flow between the subpopulations.
The best available abundance estimate for the West Indies group of breeding aggregations is 10,752 in 1992-93 (CV 0.068) with an estimated annual rate of increase of 3.1% (SE 0.5%) (Stevick et al. 2003). There is no estimate of abundance for the Cape Verde Islands breeding aggregation, but to date a total of 72 individuals have been identified there (J. Allen pers. comm. 2007). As of 2007, only one photographic match has been made from the Cape Verde Islands to a feeding ground (off Iceland), but the matching exercise is only partially complete.
Animals from the West Indies breeding area are found in all six known feeding aggregations. However, genetic evidence suggests that part of the Icelandic and Norwegian feeding aggregations consists of whales that winter outside the West Indies. Though some of these likely migrate to the Cape Verde Islands, the population found there in winter is too small relative to the number of animals thought to be breeding somewhere other than the West Indies, and at present the identity of this additional breeding area (or areas) remains unresolved.
Higher rates of increase have been estimated in some feeding areas (e.g. 6.5% for the Gulf of Maine; Barlow and Clapham 1997).
Humpbacks were heavily exploited in the past by pre-modern whaling in their breeding grounds in both the West Indies and the Cape Verde Islands, and by modern whaling in their feeding grounds, especially off Iceland and Norway in the late 19th and early 20th centuries. Catches by pre-modern whaling are estimated primarily from logbook and trade records. Catches by early modern whaling also need to be estimated because most of the catch records during the first few decades were not divided by species.
Catches in the West Indies (including Bermuda) are documented from 1664 to the present day, but the main period was 1826-1928, during which about 8,600 whales were estimated to have been killed. Whaling in the Cape Verde Islands occurred primarily during 1850-1912 with a total estimated kill of about 3,000 animals. An estimated 3,200 were taken from Iceland and 2,000 from northern Norway during 1880-1916. About 1,500 Humpback Whales are reported killed in the North Atlantic since 1916, from a variety of areas including the British Isles, Faeroes, Norway, Iceland, Greenland, and eastern Canada, as well as Norwegian pelagic catches.
Population modelling exercises show that the recent abundance and increase rate of humpback whales in the North Atlantic are too large to represent a recovery from depletion by the estimated past kills. This suggests that either:
(i) past kills have been substantially underestimated; or
(ii) there has been some increase in the environmental carrying capacity for humpback whales; or
(iii) whaling had a negative impact on the population, over and above the effects of the actual removals, in ways that are not understood; or
(iv) some combination of the above factors.
Whichever of the above hypotheses pertain, the increase rate of 3% per annum implies that humpbacks are considerably more abundant in the North Atlantic today than they were in 1940. This is consistent with anecdotal evidence of the relatively low numbers observed prior to 1960.
The following subpopulations have been identified (Calambokidis et al. 2001, 2008):
There are two additional subpopulations, one that winters off Central America and summers off California, the other that winters around the Revillagigedo Islands and summers in unknown areas but possibly in the Bering Sea or near the Aleutian Islands (Urbán et al. 2000)
Some interchange of individuals between the known North Pacific breeding grounds has been documented (Calambokidis et al. 2001, 2008).
Abundance: Eastern North Pacific. Recent information is summarized in the NOAA stock assessment report (Anon. 2005a). The abundance of humpbacks was estimated from shipboard line transect surveys in the waters of California, Oregon and Washington during 1996-2001 to be 1,314 (CV 0.30) animals. Mark-recapture from photo-identification in the same area yielded an estimate of 1,391 whales in 2002/03, with an increase of about 8% per year over the period 1991-2003. Mark-recapture from photo-identification in the Mexican Pacific yielded an estimate of 1,813 (CI: 918-2505) for the Mainland Mexico and Baja California subpopulation, and 914 (CI: 590-1193) for the Revillagigedo subpopulation (Urbán et al. 1999). The recently completed SPLASH (Structure of Populations, Levels of Abundance and Status of Humpback Whales in the North Pacific) project resulted in estimates by various methods of ~1,400-1,700 for the California-Oregon feeding area and ~6,000-7,000 for the Mexican wintering areas (Calambokidis et al. 2008).
Abundance: Central North Pacific. Based on mark-recapture analysis of photo-identification data in the Hawaiian wintering ground, the abundance was estimated at 4,005 (CV 0.095) whales in 1993 (Calambokidis et al. 1997). Older mark-recapture estimates for this stock exist, but their lack of comparability renders their use for estimating an increase rate questionable. Aerial surveys designed to be comparable across years yielded a trend estimate of 7% per year from 1993-2000 (Angliss and Outlaw 2005). SPLASH yielded wintering estimates for the Hawaii wintering ground by various methods of 7,120-10,425 (Calambokidis et al. 2008).
Summer feeding areas for this stock have been identified in Prince William Sound (Alaska), southeastern Alaska and off British Columbia, but the abundance estimates for the known feeding grounds total only about 2,000 (Angliss and Outlaw 2005a). This suggests that more feeding areas are yet to be found. In view of their current high abundance in the Hawaiian Islands, the sparseness of historical accounts of humpback whales in Hawaii prior to the 20th century is surprising. It may be a relatively new wintering ground (Herman 1979). The SPLASH estimates for the combined Southeast Alaska and British Columbia feeding areas are around 3,000-5,000 (Calambokidis et al. 2008)
Abundance: Western North Pacific. Abundance in 1991-93 was estimated at 394 (CV 0.084) from photo-identification data (Angliss and Outlaw 2005b). Humpback whale sightings from Japanese cetacean surveys in the western North Pacific, including those conducted in conjunction with the Japanese scientific whaling programme (JARPN), have not yet been analyzed to provide abundance estimates. The recent SPLASH survey covered the range more broadly and resulted in estimates by various methods of 938-1,107 (Calambokidis et al. 2008)
Humpback Whales were severely depleted by whaling throughout the North Pacific until they were protected by the IWC from 1966 onwards. Illegal Soviet catches continued until 1971 (Doroshenko 2000). Humpbacks were taken by pre-modern whalers in Japan before the 20th century, but so far no series of catch estimates have been compiled for the pre-modern period. About 21,000 humpback whales are recorded caught by modern whaling in the North Pacific in the 20th century, of which about 14,000 were in the eastern North Pacific and 7,000 in the west (IWC 2006a). Included in these figures are about 2,500 humpbacks taken illegally by USSR fleets during 1961-65, that were concealed at the time, mainly in the Gulf of Alaska and the Bering Sea (Doroshenko 2000). In addition, nearly 20,000 unspecified whales were caught in the early 20th century, of which a substantial number probably were humpbacks. The latter were taken primarily in the eastern North Pacific, except that the locations of about 9,000 unspecified whales taken by American pelagic whalers during 1911-1919 have not yet been ascertained.
No comprehensive assessment of North Pacific humpback whales has been conducted by the IWC Scientific Committee. The evidence suggests that North Pacific Humpback Whales have been increasing, following depletion by whaling, but that this recovery is not yet complete. Given catches of nearly 7,500 during 1961-65, a minimum estimate for the 1960 population would be about 8,000, but the population level in 1940 was probably lower than today. A large-scale international collaboration (the SPLASH project) involving photo-identification and genetic sampling was conducted across the entire North Pacific in 2004-06. The results have been recently analyzed and yielded a best estimate for the entire North Pacific of 18,302 (average of estimates of 17,558 for wintering and 19,056 for summer feeding areas). A 4.9% annual increase is suggested for the period since 1991-93.
The low SPLASH population estimate for the western North Pacific subpopulation of around 1,000 is a cause for concern.
Northern Indian Ocean
A resident stock, which apparently does not migrate, is found in the Arabian Sea. Genetic differences, and the lack of photographic matches with other areas, suggest that this is an isolated subpopulation; in addition, analysis of illegal Soviet catch data from the 1960s indicates that this population has a distinctly boreal reproductive cycle (Mikhalev 1997). A population estimate of 56 animals (95% CI 35-255) from photo-identification data may be negatively biased due to incomplete coverage (IWC 2005). A total of 242 whales was taken illegally by Soviet whalers in 1965-66 (Mikhalev 1997).
A comprehensive assessment of Southern Hemisphere Humpback Whales by the IWC Scientific Committee is nearing completion (IWC 2005, 2006b, 2007). Traditionally the IWC managed humpback whale stocks on the basis of the six Antarctic Areas (I through VI) but the Scientific Committee now recognizes seven major breeding stocks, A through G, some of which are tentatively further subdivided into substocks.
The wintering grounds of these are:
A (Southwest Atlantic): coast of Brazil
B (Southeast Atlantic): the coast of West Africa from the Gulf of Guinea down to South Africa
C (southwestern Indian Ocean): coasts of eastern South Africa, Mozambique, Madagascar (southern, western and eastern coasts), Mayotte, the Comoros and other western Indian Ocean island groups;
D (southeastern Indian Ocean): northwestern Australia
E (southwest Pacific) northeastern Australia, New Caledonia, Tonga and Fiji.
F (central South Pacific): Cook Islands and French Polynesia
G (southeast Pacific): Ecuador, Galápagos, Colombia, Panama and Costa Rica.
Apart from stocks A and D, there is evidence of substructure within the stocks, with subunits that are spatially and genetically isolated to varying degrees.
The extent of mixing of the C stock wintering off the coasts of Mozambique (the C1 substock), Madagascar (the C3 substock) and the western Indian Ocean island groups (the C2 substock) remains unclear.
The structure of stocks E and F is particularly unclear: there appear to be at least six separate subpopulations (eastern Australia, New Caledonia, Fiji, Tonga, Cook Islands, and islands further east), and it is unclear how these should be grouped if at all.
The structure of stock B is also unclear: there appears to a northern substock (B1) wintering off the coast off Gabon, the Congos and Cabinda (Angola) and in the Bight of Benin, and a southern substock (B2) with a diffuse or ill-defined wintering area off southern Angola, Namibia, and western South Africa, although animals seen in the southern area may include those on migration to and from wintering grounds to the north. Feeding occurs in the Benguela Current area; this may include animals wintering there but also animals stopping to feed during their migration.
The winter distribution of the G stock extends into the Northern Hemisphere, and may overlap with the distribution of North Pacific stocks; several photo-id matches have been made between the Antarctic Peninsula and Central America, although whether there is temporal overlap between these whales and their northern conspecifics is unclear. Tourist observations of mother-calf pairs around the Galápagos during January to March, if confirmed, suggest that North Pacific animals may also use this area. Phylogenetic analyses (Baker et al. 1994) reveal that maternal lineages in the eastern Pacific cross between the Northern and Southern Hemisphere populations, such that there has been some interchange between the hemispheres, but not necessarily in recent times.
For most of the breeding stocks, recent estimates of abundance on their wintering grounds have been obtained from line-transect surveys and/or capture-recapture analyses using photo-identification data. For some stocks, direct estimates of the rate of increase are available from recent time-series of abundance data. The available estimates of recent abundance and trends for wintering grounds are listed in Table 1 (see supplementary material). The total estimate of 36,600 for the Southern Hemisphere is negatively biased, because no abundance estimate is available for stock F, and the estimate for stock B covers only part of the wintering range for a discrete period. Furthermore, it is possible that the entire population does not migrate to the wintering grounds, as evidenced by, for example, an apparent excess of males in winter censuses. Rate of increase estimates are available for five stocks, ranging from 4.6% p.a. to 10.5% p.a.
The abundance of Humpback Whales during summer in the Antarctic south of 60°S has also been estimated from data from the International Decade of Cetacean Research (IDCR) (later Southern Ocean Whale and Ecosystem Research, SOWER) programme surveys. A part of the Antarctic has been surveyed each year since 1978/79, yielding 3 sets of circumpolar surveys. The abundance estimates for each circumpolar survey are listed in Table 2 (see supplementary material). All three circumpolar estimates are probably underestimates of the hemispheric population, because not all humpback whales will have been south of 60°S during the surveys, and major summer concentration areas north of 60°S in the South Atlantic (to the east of South Georgia and in the vicinity of the South Sandwich Islands and around Bouvet Island) are not included.
The summer feeding areas of each stock cannot be delineated with much precision, but a combination of photo-identification, genetic, satellite tracking and old Discovery mark data suggest the following relationships: Breeding stock A (Brazil) feeds in the South Georgia/South Sandwich area in Area II (Zerbini et al. 2006); breeding stock D (W. Australia) feeds in Antarctic Area IV ands perhaps eastern Area III; breeding stock G (southeast Pacific) feeds along the Antarctic Peninsula and around the South Shetlands, and in the Magellan Strait; breeding stock E (eastern Australia and at least some island groups of western Oceania) feeds in Antarctic Area V. The feeding areas of the other stocks could not be delineated at this stage.
Humpback Whale stocks were heavily depleted throughout most the Southern Hemisphere in the early 20th century by a combination of coastal catches in their wintering grounds and catches from land stations and by pelagic fleets in their Antarctic feeding grounds. Approximately 220,000 Humpback Whales were taken in total, of which about 100,000 since 1940; almost half of these latter consisted of illegal takes by the USSR (Zemsky et al. 1996, Allison 2006).
During 1908-1963, recorded catches outside the Antarctic (north of 40°S) have been: about 30,000 off the western coasts of southern Africa (primarily Gabon and Angola); nearly 20,000 off the eastern coasts of southern Africa (Natal, Mozambique and Madagascar) and in the western Indian Ocean; 28,000 off western Australia; about 15,000 off eastern Australia, New Zealand and southwest Pacific Islands; and about 2,000 each from the western and eastern coasts of South America. After 1904, a further approximately 27,000 whales were taken from land stations in South Georgia and over 12,000 from the South Shetlands. Pelagic whaling fleets operated during 1925-66, taking over 83,000 humpbacks. This includes more than 48,000 animals taken by the USSR, of which all but 2,710 were taken illegally (primarily from Areas IV and V); of this total, some 25,000 Soviet catches were taken in just two whaling seasons (1959/60 and 1960/61).
Due partly to the difficulties of assigning feeding areas, and hence past catches, to breeding stocks, the IWC Scientific Committee has completed population assessments only for stocks A, D, and G. The assessment of D was considered preliminary due to likely mixing in the feeding grounds with stock E and possibly other stocks.
The A stock (southwest Atlantic) is estimated to have been depleted rapidly from an initial level of 25,000 in 1904 to less than 2,000 in the 1920s, by catches from South Georgia land stations. Continued catches from South Georgia and pelagic fleets further depleted the stock to a few hundred animals by the mid-1960s when whaling ceased. The stock has recovered strongly since then to over 6,500 today.
The B stock (southeast Atlantic) was depleted by large catches in its wintering grounds off Gabon, Congo, Angola, Namibia and western South Africa, with open-boat whaling beginning in the 19th century and modern whaling beginning in 1909. Catches in Gabon and Congo were not continuous, but occurred in bursts as the stock(s) apparently began to recover between periods of intensive whaling. Nearly 30,000 humpbacks are recorded caught off the western coasts of sub-Saharan Africa during 1909-1960. The last large catches were made by Norwegian and French whalers off Gabon and São Tomé who took over 4,000 humpbacks during 1951-54. A final attempt at commercial exploitation in 1959 off Gabon caught just 160 whales.
After an initial burst of heavy catching off Mozambique and South Africa totalling nearly 8,000 whales during 1908-15, the C stock (southwest Indian Ocean) was subject to continuous but relatively low catches from Natal, South Africa between 1920 and 1962 and two discrete episodes (1937-39 and 1949-50) off Madagascar (Angot 1951). While catches off Natal remained relatively low after 1915, catches were far higher during the two episodes off Madagascar. Catches by pelagic expeditions in and outside the Antarctic probably also had an impact on this stock.
The D stock (southeast Indian Ocean) is estimated to have been reduced from a pre-whaling population of about 20,000 in 1910 to about half this level by 1940, mainly by catches from and off western Australia. Following a brief respite during WWII, the stock was further depleted (notably by illegal Soviet catches) to perhaps fewer than 1,000 animals by the mid-1960s, but recovered to about 10,000 by 1999. The current population size is very likely more than the 1940 level, and very likely more than half the pre-whaling level, subject to a caveat over the potential for mixing of stock D and other stocks in the feeding grounds (IWC 2007).
The E stock (eastern Australia/western Oceania) was heavily affected not only by catches totalling nearly 15,000 during 1909-62 from shore-station whaling in eastern Australia and elsewhere, but also by Soviet illegal pelagic catches of over 30,000, taken in Area V during the late 1950s and early 1960s.
The F stock (Oceania) was not subject to whaling in its wintering grounds but was probably affected by illegal Soviet catches in Areas V and VI. However, because the migratory destinations of this stock are unclear, assignment of these catches to the F stock has been difficult.
The G stock (southeast Pacific) is estimated to have been rapidly depleted from a pre-whaling level of about 10,000 animals in 1910 to a few hundred animals by the mid 1920s, mainly by catches from land stations on the South Shetland Islands. Pelagic catches in the putative feeding ground of this stock (Antarctic Area I) were relatively few, because of its distance from ports of approach, and because pelagic whaling was prohibited in Antarctic Areas I and VI (the then-Sanctuary) from 1935-55. The stock is estimated to have increased during 1925-55, but to have been knocked back down to the low hundreds by a new wave of pelagic catching that followed the opening of the Sanctuary in 1955. The stock is estimated to have increased since the end of humpback whaling in the mid-1960s, to its current level of about 4,000, which is well above the 1940s level but well below the pre-whaling level.
Generation time: 22 years (Taylor et al. 2007). The time window for applying the reduction criterion (A1) for a threatened category is 1941-2007.
Global population. All the new assessments of humpback whale stocks conducted by the IWC Scientific Committee to date indicate that the stocks concerned have recovered to levels at or above their 1940 level. Because the IWC Scientific Committee has not yet conducted assessments for the North Pacific and for four of the seven recognized Southern Hemisphere stocks, it is not yet possible to formally gauge the world population level relative to the 1940 level. However, given the increase rates observed in several of the unassessed North Pacific and Southern Hemisphere stocks (Table 1; see supplementary material), there is little reason to suppose that the world population is still below 50% of the 1940 level (the threshold for Vulnerable status under the reduction criterion)
Despite the encouraging global status, concern remains about apparently discrete and small subpopulations of humpback whales for which information about their status is lacking; these include the Arabian Sea (isolated from the southern Indian Ocean), the western North Pacific, and South Pacific subpopulations in portions of Oceania (breeding stocks E and F).
|Current Population Trend:||Increasing|
|Habitat and Ecology:||With few exceptions, such as the Arabian Sea population, humpback whales undertake long migrations between breeding grounds in tropical coastal waters in winter to feeding grounds in middle and high latitudes, mainly in continental shelf waters (Clapham 2002).
In the Southern Hemisphere, humpbacks appear to feed mainly in the Antarctic, where the diet consists almost exclusively of krill (Euphausia superba) (Mackintosh 1970), although some feeding in the Benguela Current ecosystem on the migration route west of South Africa has been observed (Best et al. 1995; suspected prey species are: E. lucens and Themisto gaudichaudii).
Limited data on diet in other areas is available. Humpback Whales caught off Newfoundland and Labrador in the 1950s and 1960s were found to be consuming mainly Capelin (Mallotus villotus) (Mitchell 1973). Those caught off California in the early 20th century were eating mainly euphausiids and sardines (Clapham et al. 1997). In areas of Alaska and the North Atlantic, Humpback Whales have also been observed feeding co-operatively on schools of Herring (Clupea harengus), Sand Lance (Ammodytes spp.) and (more rarely) Mackerel (Scomber scombrus), by herding the school together with bubble nets, clouds or curtains (Hain et al. 1982).
The timing of acquisition of tooth rake marks attributable to Killer Whales (Orcinus orca) indicates that Humpback Whale calves, but usually not subadults and adults, are subject to predation by this species (Mehta et al. 2005).
|Use and Trade:||Large-scale harvesting of this species has ceased, but low-level hunting continues in a few places.|
Although commercial whaling seriously depleted all humpback populations, the species has demonstrated remarkable resilience, and most populations have increased since the end of whaling, although there are several populations that remain small and for which no increase has yet been detected, such as the population in the Arabian Sea, the population breeding near South Pacific islands, and the western North Pacific population. Humpback whales have been protected from commercial whaling worldwide since 1966, and there have been few catches since 1968.
Today, small numbers only are taken by a 'subsistence' whaling operation off St Vincent (1-2 animals per year); it is possible that other small unreported catches occur elsewhere.
The government of Japan announced plans to resume humpback whaling in the Antarctic from the 2007/08 season, starting with an experimental catch of 50 animals per year under scientific permit (Government of Japan 2005). The impact of these catches on small unrecovered stocks of humpbacks in Oceania that feed in the whaling grounds of Area V is not clear.
Also, in humpback habitat off the coasts of Brazil, Gabon, Angola, Mozambique and Madagascar (Breeding Stocks A, B, and C), there is a great deal of ongoing and planned offshore oil and gas development, with potential impacts.
Humpback Whales are subject to entanglements, often fatal, in fishing gear. They are also vulnerable to injury by ship strikes, which can also be fatal. The documentation of such incidents is best for US waters. For the Atlantic coasts of the US during 1999-2003, there were 19 reports of death or serious injury caused by entanglements and seven cases of death or serious injury due to ship strikes (Anon. 2005b). For US Pacific waters (mainly Alaska) during 1999-2001 there were 13 reports of deaths and serious injuries due to entanglement and 3 reports of deaths due to ship strikes (Anon. 2005a).
Japanese Annual Progress Reports submitted to the IWC during 2003-06 listed 3-5 Humpback Whales caught annually in fishing gear, mainly coastal trap nets (Miyashita and Kato 2006).
In most areas, the observed increases in Humpback Whale abundance in recent times implies that human-caused mortality is not sufficient to threaten the populations concerned. However, the situation should be kept under review for populations that are still small and for which no increase has been detected, such as the in western North Pacific and parts of Oceania.
Humpbacks have been protected from commercial whaling in the North Atlantic by the IWC since 1955, in the Southern Hemisphere since 1963 (although spatial and temporal regulation of catches in the Antarctic occurred prior to this), and in the North Pacific since 1966. The last substantial catches occurred in 1968. Despite having been severely depleted to a world population in the low thousands at that time, humpbacks have since recovered strongly to a world population that is estimated at over 60,000 animals and is increasing.
Humpback Whales enjoy additional protective measures, such as sanctuaries, in a number of countries. The species is listed in Appendix I of both CITES and CMS.
Allison, C. 2006. Creation of the S. Hemisphere humpback catch series. February 2006. IWC Scientific Committee, Hobart, IN, USA.
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|Citation:||Reilly, S.B., Bannister, J.L., Best, P.B., Brown, M., Brownell Jr., R.L., Butterworth, D.S., Clapham, P.J., Cooke, J., Donovan, G.P., Urbán, J. & Zerbini, A.N. 2008. Megaptera novaeangliae. The IUCN Red List of Threatened Species 2008: e.T13006A3405371. . Downloaded on 30 May 2016.|