Humpback Whale

Updated: July 2018

The humpback whale is a baleen whale of the family Balaenopteridae. The Balaenopteridae include such species as the blue (Balaenoptera musculus), minke (B. acutorostrata) and fin (B. physalus) whales, and are characterized by their large size (the blue whale is the largest animal that has ever lived), ventral grooves which allow the mouth to expand, streamlined shape, high swimming speed and relatively short baleen plates. Humpback whales arch their backs at the sea surface when initiating a dive, which is the origin of the common name for the species. The genus name Megaptera means “large wing” in Greek, and describes the very large pectoral fins, which are about 1/3 the body length, the largest of any whale. The pectoral fins are mostly white in colour and easily distinguish humpbacks from other large whales. Males and females are similar in body form, coloration and size, although females are slightly larger than males.

Distribution of humpback whales in the North Atlantic (light green). Orange indicates breeding & calving areas, dark green indicates feeding areas.
Summer sightings of humpback whales during all NASS from 1987-2015. Black lines indicate areas surveyed (not all areas surveyed in each year).

ABUNDANCE

At least 22,000 in the North Atlantic

DISTRIBUTION

Found worldwide except for the very high Arctic. Humpbacks in the North Atlantic migrate between breeding grounds in the tropics (Caribbean) and feeding grounds as far north as northern Norway.

RELATION TO HUMANS

Long history of exploitation by both subsistence and commercial whaling. Hunted today in Greenland and in St Vincent and the Grenadines.

Popular target of whale-watching operations.

CONSERVATION AND MANAGEMENT

Populations increasing where data is available; e.g., increases of 12% per year off Iceland between 1986-2001 and 9.4% per year off West Greenland between 1984-2007.

International management jurisdiction of the International Whaling Commission (IWC) and NAMMCO. NAMMCO provides scientific advice on stock status and sustainable takes, and proposals for conservation and management to member governments. The IWC gives advice on sustainability of quotas.

humpback_assessment_table
humpback whale

© Fernando Ugarte

Latin name: Megaptera novaengliae

Norwegian: Knølhval
Icelandic: Hnúfubakur
Faroese: Kúlubøka
Greenlandic: Qipoqqaq
Danish: Pukkelhval
English: Humpback whale

Lifespan

Humpback whales live up to about 70 years of age

Size

Humpback whales reach a maximum length of about 17 m and a maximum weight of about 36 tonnes, although the average size is smaller than this. Females grow to a slightly larger size than males. Calves are about 6 m and 1.8 tonnes at birth

Productivity

Humpback whales reach sexual maturity at 4 to 7 years of age, and give birth to a single calf every 2 to 3 years on average. Calves are born after a gestation of 11 – 12 months, nurse for 6 months to a year and are independent after about a year

Migration

Humpback whales are long-distance travellers, making the longest annual migrations of any mammal. In the North Atlantic, they migrate annually between tropical breeding and mating areas occupied in the late winter and spring, to high latitude feeding areas in the summer, fall and early winter. The annual return trip between feeding and breeding areas can exceed 15,000 km

Feeding

Humpback whales feed by engulfing a large quantity of water that contains their prey, unfolding their ventral grooves to expand their mouth cavity, then expelling the water through the baleen, which filters out the prey items, which are then swallowed. In the North Atlantic, humpback whales feed mainly on euphausiids (krill), small schooling fish such as capelin (Mallotus villosus), Atlantic herring (Clupea harengus), sand eels (Ammodytes spp.), and mackerel (Scomber spp.)

© Fernando Ugarte

© Fernando Ugarte

General Characteristics

The humpback whale is a baleen whale of the family Balaenopteridae. The Balaenopteridae include such species as the blue (Balaenoptera musculus), minke (B. acutorostrata) and fin (B. physalus) whales, and are characterized by their large size (the blue whale is the largest animal that has ever lived), ventral grooves which allow the mouth to expand, streamlined shape, high swimming speed and relatively short baleen plates. Humpback whales arch their backs at the sea surface when initiating a dive, which is the origin of the common name for the species. The genus name Megaptera means “large wing” in Greek, and describes the very large pectoral fins, which are about 1/3 the body length, the largest of any whale.

Humpback whales are quite variable in colouration, but are usually dark grey or nearly black dorsally, with some white patterning on their flukes and pectoral fins. The white markings combined with nicks and gouges on the flukes are individually distinctive and are frequently used to identify individual animals (e.g. Smith et al. 1999). The ventral side is much lighter in colour and sometimes mostly white. The ventral grooves run from the ventral rostrum for about half the body length. The head and lower jaw are covered in knobbly hair follicles called tubercles, and also often host a heavy growth of barnacles.

humpback whale tubercles

Humpback whale showing the knobby “tubercles” on the rostrum (nose). © Fernando Ugarte

Humpback whales reach a maximum length of about 17 m and a maximum weight of about 36 tonnes, although the average size is smaller than this. Females grow to a slightly larger size than males (Bettridge et al. 2015).  Calves are born after a gestation of 11 – 12 months and are about 6 m and 1.8 tonnes at birth. Calves nurse for 6 months to a year and are independent after about a year.

Humpback whales are long-distance travellers, making the longest annual migrations of any mammal. In the North Atlantic, they migrate annually between tropical breeding and mating areas in the late winter and spring, to high latitude feeding areas in the summer, fall and early winter. The annual return trip between feeding and breeding areas can exceed 15,000 km. However humpback whales are not fast swimmers compared to other members of their family, normally travelling between 2 – 12 km per hour and up to 200 km per day during migration (Heide-Jørgensen and Laidre 2007, Ford and Reeves 2008).

Humpback whales reach sexual maturity at 4 to 7 years of age, and give birth to a single calf every 2 to 3 years on average (IWC 2002, NAMMCO 2009). Their only known predator is the killer whale (Orcinus orca), which probably take mainly calves in the North Atlantic (Ford and Reeves 2008).

Humpback whales are a favourite of whale-watchers, as they are very active at the surface, often breaching, rolling and gulping prey. They often engage in group feeding behaviour. Humpbacks make a wide variety of sounds but are known for their highly varied and characteristic “songs” which may last 20 minutes or more and are distinctive to stocks (Bettridge et al. 2015).

Listen to humpback whale songs on their breeding grounds in the Silver Banks

Life History and Ecology

As members of the family Balaenopteridae, humpback whales are “baleen” whales. Baleen is composed of plates of a keratin, a fibrous structural protein that also is found in fingernails, claws and hair. These plates hang down from the upper jaw, taking the place of teeth in baleen whales. Baleen plates are fringed by fine hairs that form a fibrous filter when the plates are extended. Baleen whales feed by engulfing a large quantity of water that contains their prey, unfolding their ventral grooves to expand their mouth cavity, then expelling the water through the baleen, which filters out the prey items, which are then swallowed.

© NOAA

© NOAA

The humpback whale is a medium-sized baleen whale, smaller than the blue, fin, right or bowhead whales but larger than sei or minke whales. Calves are born in tropical waters after a gestation period of 11-12 months. Mating occurs in the same area, however females who have given birth do not usually mate in the same year, leading to a calving interval of 2 – 3 years. Males and females reach sexual maturity at an age of 5 – 7 years, and may live up to about 70 years. Calves rely on their mothers for milk for about the first six months of their lives, and are weaned and independent at one year of age (IWC 2002, Bettridge et al. 2015, Clapham et al. 2003).

Male humpbacks also travel to the tropical breeding grounds in most years, where they compete with one another to mate with receptive females. Males are polygynous, meaning that they may mate with several females in a single season. Humpback whales are well known for their songs, which are composed of individual spaced elements and may last 10 -20 minutes and can be heard by other whales at distances of up to 50 km (Bettridge et al. 2015). Only males sing, and they do so primarily (but not always) during the mating season. The song is repeated, often for hours on end, and each song is characteristic of the mating group, or stock. Songs do not vary much between individuals but do evolve over the course of months or years. The function of humpback whale song is clearly related to mating. It may serve as a secondary sexual characteristics, with females choosing the male with the most desirable song. Alternately, singing may be a competitive, antagonistic interaction among males vying for mates, or may serve to space males on the breeding ground.

Males often compete aggressively during the mating season, often butting heads or ramming one another, or hitting each other with their flukes or flippers. The tubercles, the hard, knobby growths on the head, lower jaw, fins and flukes may serve a role as weapons in this aggression. They are often encrusted with barnacles: a single whale may carry as much as 450 kg of barnacles! The hard, sharp barnacle encrustation may serve to enhance the effect of a blow, whether in competition with another male or in defence against a predator (Ford and Reeves 2008).

During most times of the year, humpback whales are found in small groups of 2 – 5 animals. Sometimes larger groups form temporarily to engage in cooperative feeding on prey aggregations. Groups of up to 95 animals have been spotted off West Greenland, but the function of these very large groups is unknown (Heide-Jørgensen et al. 2008).

Migrations

Humpback whales are the mammalian champions of migration, travelling up to 15,000 km per year between their tropical breeding/mating area and their high latitude feeding grounds. They arrive at the breeding grounds in February, and most are gone by the end of April (Stevick et al. 2016). Breeding grounds are found around tropical islands and are usually in fairly shallow waters, close to shore or associated with offshore reefs (IWC 2002). Most animals use the same breeding ground throughout their lives, however recently some exchange between breeding grounds has been observed (Stevick et al. 2016).

Humpback whales begin to arrive at their northerly feeding grounds in May. Six feeding grounds have been identified; these range in latitude from 43° (Gulf of Maine) to the northern Norwegian and Barents Seas (75°). Similarly the migration distance varies from less than 1,000 km from the Gulf of Maine to over 7,000 km for North Norway. Most whales appear to use the same feeding ground year after year, and may even return to the same bay or fjord repeatedly (IWC 2002, Boye et al. 2010). Although humpback whales are not fast swimmers compared to some other baleen whales, migration between the breeding and feeding grounds can be quite rapid, with animals often travelling over 200 km per day for several weeks to complete the journey (Heide-Jørgensen and Laidre 2007, Kennedy et al. 2013, NAMMCO 2015). The complete round trip from the Norwegian feeding ground to the Caribbean breeding ground may take more than five months (Kennedy et al. 2013). Feeding grounds typically occur in areas where water masses mix, causing upwelling and leading to high productivity. This leads to concentrations of pelagic crustaceans and small fish, enabling the whales to feed effectively.

Not all humpback whales make the return trip from the feeding grounds to the breeding grounds every year. Some linger on the Icelandic feeding ground throughout the entire winter, following the migrating capelin (Mallotus villosus) (Magnusdóttir et al. 2014). ). Humpback whales have also been recorded throughout the winter off Greenland, Norway and the British Isles (IWC 2002, Heide-Jørgensen and Laidre 2007, Smith and Pike 2009). Humpback whale songs have also been recorded in some of these areas, suggesting that mating activity may be taking place. There is also some evidence that the migratory behaviour of humpback whales has changed in historical times. Whaling records indicate that that the principal Caribbean breeding ground occurred much farther south in the Windward Islands, an area with few breeding whales today (Smith and Reeves 2011). Presently the breeding ground lies farther north off the Dominican Republic and Puerto Rico (Smith et al. 1999). A large number of whales were also taken on the Cape Verde breeding ground, and area that holds few whales today (Smith and Reeves 2011, Reilly et al. 2008, Wenzel et al. 2009). In recent years, humpback whales have begun to occur in fjords in Northern Norway, where they were completely absent less than 10 years ago. The migratory behaviour of humpback whales therefore has a degree of flexibility, with some animals apparently not migrating in some years, and migratory patterns changing over decades, perhaps in response to changes in prey distribution or other factors.

Diet and Feeding

Humpback whales have a diverse diet and exhibit great flexibility and variation in their feeding behaviour. They prefer to feed on prey that has been naturally concentrated by currents and upwelling or by spawning and migratory behaviour. They also use their maneuverability and social cooperation to further concentrate and trap prey animals, making their feeding more efficient.

Humpback whales feeding off the coast of Norway. © Fernando Ugarte

Humpback whales feeding off the coast of Norway. © Fernando Ugarte

In the North Atlantic, humpback whales feed mainly on euphausiids (krill), small schooling fish such as capelin (Mallotus villosus), Atlantic herring (Clupea harengus), sand eels (Ammodytes spp.), and mackerel (Scomber spp.). The diet varies by season and feeding ground depending on the availability of suitable prey. In the Gulf of Maine, humpback whales feed on spawning herring which form large dense schools at night (Gong et al.  2014). Off Greenland and Iceland they feed primarily on euphausiids, capelin and sand eels (Heide-Jørgensen and Laidre 2007, Heide-Jørgensen and Simon 2007, Magnusdóttir et al. 2014). Humpbacks appear to track the movements of their prey and change their distribution in response to changes in the abundance and distribution of prey species. For example the distribution of humpbacks has changed greatly around Iceland and northern Norway in recent years, apparently in response to changes in the distribution of capelin and herring (Víkingsson et al. 2015).

Watch humpback whales in Northern Norway under the Northern Lights

Watch a video of humpback whales taken by the Institute of Marine Research

During the breeding season, humpbacks do not feed, surviving on their stored blubber reserves. These tropical waters do not host the concentrated schools of invertebrates or fish that humpbacks require for efficient feeding.

Feeding dives may last as long as 16 minutes, but are usually much shorter (Heide-Jørgensen and Laidre 2007). Feeding depth varies with the distribution of the prey but seldom exceeds about 200 m.

Humpback whales have a much more varied repertoire of feeding behaviours than other baleen whales. Humpbacks forage singly or in groups. The most common feeding mode is “lunge feeding”, in which the whale accelerates rapidly forward (lunges), opening its mouth, expanding its buccal cavity by stretching out the ventral grooves, and engulfing a volume of prey-laden water that can exceed its own weight (Simon et al. 2012). The whale then expels this water through its baleen to filter out the prey, which is then swallowed.

Humpbacks may be the only cetaceans to engage in a form of tool use. They use their expelled air to create walls or nets of bubbles with which they corral and herd schools of fish. They often do this in small groups, cooperating to concentrate their prey, then engulfing it. This often results in spectacular surface displays, with groups of humpbacks breaching the surface as they engulf schooling fish, amidst a roiling cloud of bubbles (Bettridge et al. 2015). These are behaviours that must be learned and practiced, implying a relatively high degree of cultural transmission. Feeding activity often varies with time of day, following the vertical migrations of their prey. In some areas, humpbacks dive to the bottom and roll repeatedly, likely startling bottom dwelling fish into the water column which are then engulfed. However much feeding is done near the surface, increasing the appeal of this species to whale watchers.

bubble feeding humpback whale

Humpback whale bubble feeding © Christine Khan/NOAA

Humpback whales produce a variety of sounds that are associated with feeding activity. Some of these may be used to maintain coordination during group feeding. In the Gulf of Maine, humpbacks make repeated, short clicks, termed “meows” or “megaclicks”, while feeding on schooling herring at night. One conjecture is that this is a primitive form of echolocation, or sonar, which has been previously thought to be restricted to toothed whales such as dolphins, narwhals and belugas. The sounds are of a frequency range and duration suitable for the acoustic detection of fish schools. However, as this behaviour has not been directly observed, it remains uncertain whether this is true echolocation or perhaps some form of communication or signalling between individuals (Gong et al. 2014).

Predators

As one of the largest animals on earth, an adult humpback whale is a formidable opponent for any predator. Calves are however more vulnerable, and there is evidence that predation by killer whales (Orcinus orca) may be significant in some areas. A relatively high proportion of animals, 20 – 40% in some areas, have rake marks on their flukes or fins that could only be made by killer whales (Ford and Reeves 2008, McCordic et al. 2014). Long-term photo-ID studies suggest that most whales get these marks when they are calves, indicating that killer whale attacks on adult animals are rare. Killer whales are largely absent from the tropical waters where humpback whales breed, so most attacks must occur on the feeding grounds or during migration. Indeed it has been suggested that the absence of killer whales may be the primary reason humpback whales use these areas for calving (Corkeron and Connor 1999).

Killer whale attacks are rarely observed, and the extent of successful predation on humpback whales is not known. While rake marks indicate that some animals survive attacks, those that don’t are obviously not observed. Humpback whales are not defenceless however: when harassed they often bunch together and fight back by slashing their tales and fins, and butting their attackers with their heads. The hard, sharp barnacles which encrust the head may serve as defensive weapons against killer whale attack: the cetacean version of the “brass knuckle” (Ford and Reeves 2014).

Encounters with killer whales do not always result in attacks. In some areas, killer and humpback whales feed together, even perhaps cooperatively, on schooling fish. However killer whales occur in several “ecotypes”, some of which do not feed on marine mammals, perhaps explaining this observation (Ford and Reeves 2014).

Breeding grounds

Humpback whales are the mammalian champions of migration, travelling up to 15,000 km per year between their tropical breeding/mating area and their high latitude feeding grounds. They arrive at the breeding grounds in February, and most are gone by the end of April (Stevick et al. 2016). Animals from the more distant feeding grounds off Northern Norway and Iceland arrive slightly later (Stevick et al. 1999). Breeding grounds are found around tropical islands and are usually in fairly shallow waters, close to shore or associated with offshore reefs (IWC 2002). Humpbacks spend the remainder of the year at northern feeding grounds, which range in latitude from 43° (Gulf of Maine) to the northern Norwegian Sea (75°). Feeding grounds typically occur in areas where water masses mix, causing upwelling and leading to high productivity. This leads to concentrations of pelagic crustaceans and small fish, enabling the whales to feed effectively. Humpback whales are largely faithful to their own feeding and breeding areas, as indicated by both photographic and genetic evidence (Smith et al. 1999), although some exchange between breeding areas has been observed (Stevick et al. 2016). They also exhibit site fidelity on a smaller spatial scale, with some animals occupying the same bay in Greenland year after year (Boye et al. 2010).

Disko_050818_FU 193

© Fernando Ugarte

Two humpback whale breeding grounds are known with certainty in the North Atlantic. The largest by far in terms of whale numbers is the West Indies ground, which most whales from all feeding grounds use (Smith et al. 1999). The area utilized by humpbacks extends from Cuba in the northwest south to Venezuela, however the largest concentrations of breeding animals are found on the Silver and Navidad Banks near the Dominican Republic, with much lower numbers in Samana Bay (Dominican Republic), off the northwest coast of Puerto Rico, and around the Virgin Islands and the eastern Antilles (Reilly et al. 2008, IWC 2002, Smith et al. 1999). Whaling records indicate that, historically, the principal Caribbean breeding ground occurred farther south in the Windward Islands, an area with few breeding whales today (Smith and Reeves 2011). However recent satellite tagging studies have shown that some whales make extensive inter-island movements in the area (Kennedy et al. 2013). The breeding area is characterized by relatively shallow water (<200 m), low slope and warm water temperatures from 24 – 28 C (Stevick et al. 2016). Humpbacks begin to arrive in this area in early February, numbers peak in late February and few whales remain by the end of March (Stevick et al.2016).

A second breeding area is found around the Cape Verde Islands off West Africa. This area hosts few whales today (Wenzel et al. 2009), but whaling records suggest that substantial numbers occurred there in the past (Smith and Reeves 2011). Only whales from the Icelandic and Norwegian feeding areas are known to use this area, but most whales from these feeding areas use the West Indies ground (Wenzel et al. 2009). This breeding ground is occupied beginning in March, a few weeks later than the West Indies ground, and peak occupation occurs in early April (Stevick et al. 2016).

While it was originally thought that humpbacks were faithful to their natal breading ground, returning to breed in the area in which they were born (IWC 2002), recently four individuals have been identified in both the West Indies and at Cape Verde in different years. This suggests a heretofore unsuspected degree of flexibility in the migratory behaviour of these animals (Stevick et al. 2016).

Other breeding grounds are suspected but not confirmed. Humpback whale song has been recorded year round in the southern Norwegian Sea, and animals with full-term fetuses were taken by whaling operations in northern Norway in the late 19th and early 20th centuries, suggesting that a breeding area may exist there (IWC 2002, Smith and Pike 2009). A third breeding ground off West Africa has also been suggested (Punt et al. 2007). There may also be finer scale partitioning on the West Indies ground, with whales from different feeding grounds using separate areas within the overall breeding area (Stevick et al. 2016).

Distribution of humpback whales in the North Atlantic (light green). Orange indicates breeding & calving areas, dark green indicates feeding areas.

Distribution of humpback whales in the North Atlantic (light green). Orange indicates breeding & calving areas, dark green indicates feeding areas.

Feeding grounds

Six discrete feeding grounds are recognized in the North Atlantic: these tend to be separated from one another by gaps of hundreds of kilometers in which few humpback whales occur (Vigness-Raposa et al. 2010). Three feeding stocks occur off Eastern North America: the Gulf of Maine/Scotian Shelf, the Gulf of St. Lawrence, and Newfoundland/Labrador. In the Central Atlantic, humpbacks feed off West Greenland and on the Icelandic continental shelf. The easternmost feeding stock occurs off Northern Norway, especially around Bear and Jan Mayen Islands (IWC 2002, Reilly et al. 2008, Smith and Pike 2009). Scattered humpback whale sightings outside of the breeding season have been reported along the Mid-Atlantic Ridge, so this represents another possible feeding ground (Smith and Pike 2009), although they might also be animals in transit from the Caribbean breeding ground to the Norwegian or Icelandic feeding grounds (Kennedy et al. 2013). Humpback whales occur in considerable numbers off East Greenland in some years, so this may be another feeding ground, or possibly animals from the West Greenland or Iceland grounds (NAMMCO 2017).

Feeding grounds typically occur in areas where water masses mix, causing upwelling and leading to high productivity. This leads to concentrations of pelagic crustaceans and small fish, enabling the whales to feed effectively (Víkingsson et al. 2015). They range in latitude from 42° (Gulf of Maine) to 75° (North Norway) and therefore encompass a wide variety of marine ecosystems, ranging from temperate to low Arctic. Humpback whales generally do not enter ice-filled waters and are therefore largely absent from the Canadian Arctic, although sightings have been reported there in recent years, probably in response to reductions in sea ice due to climate change (Higdon and Ferguson 2011).

Not all humpback whales make the return trip from the feeding grounds to the breeding grounds every year. Some linger on the Icelandic feeding ground throughout the entire winter, following the migrating capelin (Mallotus villosus) (Magnusdóttir et al. 2014). ). Humpback whales have also been recorded throughout the winter off Greenland, Norway and the British Isles (IWC 2002, Heide-Jørgensen and Laidre 2007, Smith and Pike 2009). Humpback whale songs have also been recorded in some of these areas, suggesting that mating activity may be taking place. There is also some evidence that the migratory behaviour of humpback whales has changed in historical times. Whaling records indicate that that the principal Caribbean breeding ground occurred much farther south in the Windward Islands, an area with few breeding whales today (Smith and Reeves 2011). Presently the breeding ground lies farther north off the Dominican Republic and Puerto Rico (Smith et al. 1999). A large number of whales were also taken on the Cape Verde breeding ground, and area that holds few whales today (Smith and Reeves 2011, Reilly et al. 2008, Wenzel et al. 2009). In recent years, humpback whales have begun to occur in fjords in Northern Norway, where they were completely absent less than 10 years ago. The migratory behaviour of humpback whales therefore has a degree of flexibility, with some animals apparently not migrating in some years, and migratory patterns changing over decades, perhaps in response to changes in prey distribution or other factors.

North Atlantic Stocks

To a biologist, a stock is a subpopulation of a species that is largely reproductively isolated from other stocks of the same species. As a result of this reproductive isolation, stocks can usually be differentiated genetically if they have been isolated for a sufficient length of time. Other means of stock differentiation include morphometrics (body size and shape), concentrations of pollutants or rare elements in tissues, behaviour, including vocal dialects, and patterns of seasonal movement. A key feature of this concept is that the hunting and possible depletion of one stock should have little or no effect on a neighbouring stock.

Little difference in humpback whale nuclear DNA among North Atlantic feeding areas has been detected. Whales from the Eastern Atlantic feeding grounds could be distinguished from some Western Atlantic groups (IWC 2002, Wenzel et al. 2009). However whales from all six feeding grounds can be distinguished from one another using mitochondrial DNA (Larsen et al. 1996, IWC 2002). This DNA is passed directly from mother to offspring, rather than sexually as with nuclear DNA. This suggests that humpback whales tend to use the same feeding grounds throughout their lives, leading to the differences in mitochondrial DNA, but mix with animals from other feeding grounds when mating, explaining the lack of differentiation in nuclear DNA. Such “maternally directed site fidelity” is a pattern seen in several cetacean species, including beluga and narwhal.

Photo-identification studies, in which individual whales are identified and re-sighted based on the markings on their tail flukes, suggest that humpback whales from all feeding grounds mix on the West Indies breeding ground (IWC 2002, Reilly et al. 2008). In contrast only whales from the Norwegian and Icelandic feeding areas have been traced to the Cape Verde breeding ground (Wenzel et al. 2009). Genetic studies suggest that relatively large proportions of the Icelandic and Norwegian whales do not breed in the West Indies, numbering far more than can be accounted for by the very low numbers found on the Cape Verde breeding ground (Punt et al. 2007, Wenzel et al. 2009). Again this suggests the existence of at least one more breeding ground, possibly in the southern Norwegian Sea or off West Africa (Punt et al. 2007, Smith and Pike 2009).

© Fernando Ugarte

© Fernando Ugarte

There is so far no direct evidence from photo-ID or tagging studies of any exchange of whales between feeding grounds. Recently, however, four individuals have been identified in both the West Indies and at Cape Verde in different years (Stevick et al. 2016), which suggests that humpbacks are not always faithful to their natal breeding ground. This too would help explain the lack of discrimination in nuclear DNA, if whales are occasionally exchanged between breeding grounds.

Taken together, the genetic and photo-ID evidence, along with the known migratory patterns of humpback whales, suggest that stocks can be defined by the breeding and feeding grounds of a particular group. This means that whales from the six North Atlantic feeding grounds that breed in the West Indies comprise separate stocks. Additionally, those from the Icelandic and Norwegian areas that breed at Cape Verde or some unknown breeding ground would also be separate stocks, leading to a total of at least 8 North Atlantic stocks of humpback whales. Other feeding grounds may occur off East Greenland (NAMMCO 2017) and along the mid-Atlantic Ridge (Smith and Pike 2009), suggesting the possibility of additional stocks.

Current Abundance and Trends

Counting humpback whales

Humpback whale stocks are largely isolated from one another on their feeding grounds, and can therefore be enumerated there. Humpback whales are counted using line transect surveys, either from a plane or a ship (e.g. Paxton et al. 2009). Because humpback whales can be individually identified by the unique markings on their flukes, population size can also be estimated using “mark-recapture”, or in this case “sight-resight” methodologies. A sample of whales is identified (“marked”) by photographing their flukes. A second sample of fluke photographs is collected some time (e.g. one year) later. If all assumptions are met, the proportion of “marked” whales in the second sample should equal the proportion of marked whales in the total population. An alternative method of identifying or “marking” whales is to use a biopsy dart to collect tiny skin samples, then genetic analysis to identify individuals Smith et al. (1999) applied mark-recapture methodology to the entire North Atlantic basin, collecting fluke photographs and genetic identifications at the West Indies breeding ground and all North Atlantic feeding grounds over two consecutive years, to derive an abundance estimate for the entire North Atlantic.

Feeding ground estimates

The most recent available abundance estimates from North Atlantic feeding grounds are shown in the table below. These estimates come from aerial and ship surveys, and most are underestimates because they are not corrected for whales missed by the observers (perception bias), or whales that were submerged (availability bias), or both.

The Icelandic feeding ground hosts by far the largest stock component, likely exceeding 13,000 whales. Estimates of similar magnitude have been derived from surveys conducted in 1995 and 2001 (Paxton et al. 2009). The Newfoundland/Labrador and West Greenland feeding areas hold similar numbers of between 3 and 4 thousand whales. The remaining feeding areas are smaller, all hosting less than one thousand whales. The total for all feeding areas for the period 2007 – 2011 (except Norway which is from 1996-2001) is nearly 22,000 whales: this should be considered a minimum estimate for the entire North Atlantic since most of its components are negatively biased and some areas that may also host feeding grounds, such as East Greenland (NAMMCO 2017) and the mid-Atlantic Ridge (Smith and Pike 2009) are not included.

humpback-abundance

Breeding ground and ocean basin estimates

The Years of the North Atlantic Humpback (YoNAH) project collected genetic samples and fluke photographs from all North Atlantic feeding grounds and from the West Indies breeding ground from 1992-1993, and used mark-recapture methods to estimate the total population of the North Atlantic as 10,600 (95% CI 9,300 – 12,100) (Smith et al. 1999). A similar study was conducted in 2004 – 2005, yielding an estimate of 12,312 (95% CI 8,688-15,954) (Bettridge et al. 2015). Smith and Pike (2009) noted that these estimates are substantially lower than the total of the feeding ground estimates for similar periods, which are themselves negatively biased. The YoNAH and later mark-recapture estimates may underestimate the total population because no sampling was conducted at the Cape Verde breeding ground or at other as-yet undescribed breeding grounds. The Cape Verde breeding population alone has been estimated as about 260 whales (Ryan et al. 2014), far too low to account for the discrepancy between feeding ground estimates and the ocean basin mark recapture estimates.

Trends in abundance

In areas where sufficient data are available to establish a trend, numbers of humpback whales are increasing, in some cases quite rapidly. Under ideal conditions humpback whale populations can grow at an annual rate of about 11% (Heide-Jørgensen et al. 2012). Aerial surveys conducted around Iceland between 1986 and 2001 indicated a rate of increase of about 12% per year. A similar rate of 9.4% per year has been observed off West Greenland between 1984 and 2007 (Heide-Jørgensen et al. 2012). As these are the largest feeding grounds in terms of whale numbers, these increases should result in similar increases on the breeding grounds, however numbers in the West Indies breeding ground have increased at a rate of about 2% between 1979 and 2005 (Bettridge et al. 2015). Again this suggests that a substantial proportion of whales from these feeding grounds must be utilizing a breeding ground that has not been directly enumerated.

Stock Status

Assigning a “status” to a particular stock of animals is a complex and sometimes controversial exercise that requires, among other things, some knowledge of the historical abundance trend of the stock, an assessment of the reliability of that knowledge, and clearly stated management/conservation goals with respect to the stock. There is no universal definition of stock status that is used by all organizations and countries. It is important therefore to clearly define stock status before an assignment is made.

The humpback whale is a worldwide species, occupying all world oceans on at least a seasonal basis. Globally, humpback whales have recovered more rapidly than most other baleen whales from overhunting by commercial whalers in the 20th century, probably because they were not a favoured species for whalers (Smith and Reeves 2011) and are able to increase their numbers more rapidly than most other species (Heide-Jørgensen et al. 2012). The International Union for Conservation of Nature and Natural Resources (IUCN) uses specific criteria to assign species to one of nine classifications ranging from “Least Concern” to “Vulnerable” to “Extinct” (Reilly et al. 2008). Under this system, humpback whales are classified globally as being of “Least concern” for conservation, primarily because populations are increasing in most areas where data are available, and population sizes are probably over 50% of pre-whaling levels in most areas (Reilly et al. 2008).

In the North Atlantic, a total catch (including struck and lost) of over 30,000 whales primarily between 1880 and 1940 (Smith and Reeves 2011) apparently reduced the population to a very low level at which whaling became unprofitable in most areas. Whaling has ceased or been reduced to very low levels since 1940, and there have been signs of recovery in many areas, including Iceland (Paxton et al. 2009, Pike et al. 2009), West Greenland (Heide-Jørgensen et al. 2011), the Gulf of Maine and on the West Indies breeding ground (Bettridge et al. 2015).

The Scientific Committee of the International Whaling Commission (IWC) attempted to develop an assessment model for North Atlantic humpback whales (IWC 2002, 2003). The model integrated abundance estimates for the entire North Atlantic (Smith et al. 1999) and for several feeding areas, known trends in abundance, historical harvests from all areas and known life history parameters such as reproductive and natural mortality rates. Punt et al. (2007) furthered this analysis by exploring alternative estimates of abundance and catch, as well as the possible existence of a third breeding ground. While these modelling efforts were not completely successful in providing an acceptable fit to estimated population trajectories on some of the feeding and breeding grounds, they do indicate that the North Atlantic humpback whale population has increased substantially since the cessation of whaling and may be approaching pre-whaling levels of between 20 and 26 thousand animals. The most recent data on feeding ground abundance, summing to nearly 21 thousand animals, supports this suggestion.

While humpback whales are recovering or have recovered in most areas, numbers are still very low around the Cape Verde Islands, a breeding area where several thousand whales were harvested historically. Today they number in the low hundreds (Ryan et al. 2014). There are no data on population trends in this area. A small proportion of the whales that use the Norwegian and Icelandic feeding grounds apparently breed in this area (Wenzel et al. 2009), and these stock components are therefore of conservation concern.

The Scientific Committee of NAMMCO (2009) recently carried out an assessment of the West Greenland feeding area, to determine if a proposed resumption of harvest there was sustainable. The most recent estimate of the size of this stock component is 3,272 (95% CI 1,300 – 8,233), and numbers have increased at 9.4% per year between 1984 and 2007 (Heide-Jørgensen et al. 2012). A model incorporating these data as well as historical harvests and estimates of life history parameters indicated that the stock component has likely recovered to or nearly to its historical size, and that an annual take of up to 20 whales per year would be sustainable.

© Fernando Ugarte

© Fernando Ugarte

Management

The humpback whale falls under the international management jurisdiction of the International Whaling Commission (IWC) and NAMMCO. NAMMCO provides scientific advice on stock status and sustainable takes, and proposals for conservation and management to member governments. NAMMCO is the only international government organization presently operating an international inspection and observation program for marine mammal hunts, the Joint Control Scheme for the Hunting of Marine Mammals. The Scheme contains a set of common elements for national inspection programs for coastal and offshore whaling, including items mandatory for inclusion in whaling logbooks. It also includes an International Observation Scheme, with the overall objective of monitoring whether the decisions made by NAMMCO are respected and that all national and international regulations and requirements are being met. NAMMCO appoints observers to directly oversee hunting and inspection activities in member countries. These observers, who are normally not resident in the country being observed, may go out on whaling vessels to observe hunts, check licenses and relevant certificates, and inspect whaling logbooks. An observer might also inspect landing and processing facilities. Observers report directly to the NAMMCO Secretariat.

The IWC began establishing commercial quotas for humpback whales in the 1970’s. In 1986, the IWC instituted a “temporary” moratorium on commercial whaling which continues to today. However, by this time commercial whaling for humpbacks in the North Atlantic had largely ceased. The IWC continues to provide assessment and scientific advice on humpback whale stocks in the North Atlantic.

The IWC does provide management advice for Aboriginal Subsistence Whaling. The recommended strike limits are based on scientific advice on sustainable take and the cultural and nutritional need level of the aboriginal group. The main objectives for Aboriginal Subsistence Whaling are 1) to ensure the risk of extinction is not seriously increased; 2) to enable harvests in perpetuity appropriate to cultural and nutritional requirements, and; 3) to maintain stocks at their highest net recruitment level and if below that to ensure they move towards it. Therefore, while quotas for commercial whaling are limited primarily by sustainability, allowable takes for the Aboriginal Subsistence whaling are limited both by sustainability and nutritional and cultural need.

Humpback whales continue to be hunted in two areas of the North Atlantic. On the island of Bequia, part of the country of St. Vincent and the Grenadines in the Caribbean, a small hunt (0 – 4 whales per year) for humpback whales is carried out annually. The area is in the West Indies breeding ground, so whales taken here could be from any of the North Atlantic feeding grounds. The IWC has established a block quota of 24 for the period 2013 – 2018 under the Aboriginal Subsistence Whaling management program (IWC 2015).

Humpback whaling has a long history in West Greenland, and has been conducted since the 1700’s and possibly before (Greenland 2012, Smith and Reeves 2011). Whaling for humpbacks was prohibited in 1986 as there was concern that the stock had been depleted. In 2007, Greenland requested a quota for humpback whales under the Aboriginal Subsistence Whaling management program at IWC. The Scientific Committee of the IWC completed an Aboriginal Whaling Management Procedure for humpback whales in 2008 (IWC 2008) and used it to advise that catches of 10 humpback whales per year would be sustainable. Similarly NAMMCO (2009) conducted an assessment of West Greenland humpback whales and concluded that takes of up to 20 per year would be sustainable. In 2010, Greenland implemented a catch quota of 9 humpback whales per year for West Greenland, with the possibility of carrying over up to two unused quota animals from one year to the next (Greenland 2012).

In Greenland the Ministry of Fisheries, Hunting and Agriculture has authority over whale hunting. The taking of humpback whales is limited to full-time hunters who have a valid permit to take whales. All prospective hunters must take a course on the handling of the harpoon cannon and whale grenades. Regulations limit the hunt to vessels at least 36 feet in length equipped with a harpoon cannon. The harpoon cannon must be inspected every second year. Locally, wildlife officers monitor whale hunts and ensure that all requirements are met. Once a whale is caught, the hunter is responsible for providing a catch report to municipal authorities, including time and location of the hunt, biological data such as length, sex, reproductive state of females, stomach contents and weight of meat products, and information on the hunt, including the number of grenades used and the estimated time to death (Greenland 2012).

Under Greenlandic law all whale products must be consumed locally and no export is permitted (Greenland 2012).

Hunting and Utilisation

Unlike the much faster fin and blue whales, the relatively slow moving humpback whale was vulnerable to whalers using only sailing ships and rowboats, and therefore has a longer history of exploitation in the North Atlantic. Greenland Inuit have taken humpback whales for at least a thousand years, hunting them from kayaks and umiaq (larger skin boats) using hand-held harpoons, floats and lances (Greenland 2012). Early Basque whalers may also have occasionally taken humpback whales, although they specialized in right, bowhead and possibly gray whales.

As with other large whales, humpbacks were hunted primarily for their oil, which was used for lighting, as a lubricant and later as a food source. The flexible baleen was also used for many purposes for which plastic might be used today, for example for buggy whips, corset stays and collar stiffeners. If processed on shore, the offal and bones were sometimes used to make fertilizer. Meat for human consumption was not an important product for early commercial whalers, but became more important in the 20th century.

Smith and Reeves (2011) provide a detailed history of humpback whaling in the North Atlantic. Historically, humpback whaling can be roughly divided into two types of fisheries: non-mechanized and mechanized. Non-mechanized whaling used sailing ships and rowboats, and the whales were struck with “cold” (non-explosive) harpoons and killed with lances. This type of whaling could be either shore-based, where the whales were taken close to the coast and towed to a station for processing, or pelagic, in which the whale was processed aboard the ship at sea. About 14,000 humpbacks were landed by non-mechanized whaling between 1600 and 1900, with most being taken in the last hundred years of the period on the breeding grounds in the West Indies and Cape Verde Islands. Struck and loss rates were relatively high in this type of whaling, estimated by Smith and Reeves (2011) as 41% of landed catch.

Mechanized whaling, using faster motorized ships and gun-fired harpoons equipped with explosive grenades, was developed by Norwegian Svend Foyn in the 1870’s. This drastically improved the efficiency and safety of whaling, and made catching the faster fin and blue whales feasible. Often led by Norwegian companies, this type of whaling rapidly spread throughout the North Atlantic, including northern Norway, Svalbard and Bear Island, Iceland, the Faroes, West Greenland, Canada, and the humpback breeding grounds at Cape Verde and the West Indies. The catch of humpbacks in mechanized whaling operations peaked around 1900, with a total of about 7,700 whales landed. Largest catches were taken in North Norway, Iceland and Newfoundland. Loss rates were much lower in mechanized whaling than in non-mechanized whaling, as the whale was killed outright or severely injured by the grenade at the same time it was secured by the harpoon. Smith and Reeves (2011) estimate that the loss rate in mechanized whaling was less than 2% of landed catch.

Whaling for humpbacks ended in most areas by around 1930, by which time most stocks were reduced to such low levels that whaling was no longer profitable. By this time also petroleum products had replaced whale oil for most non-food uses. In all, a total of 21,476 humpback whales are known to have been landed in the North Atlantic, corresponding to a total removal of 30,852 when corrected for struck and lost animals (Smith and Reeves 2011). Catches peaked in the period 1870 – 1910, corresponding to the advent of mechanized whaling operations in several areas. Some humpback whaling continued in West Greenland and in the Caribbean after 1930, but North Atlantic catches as a whole have never since approached historical levels.

Whaling in Bequia

A very small hunt for humpback whales continues in Bequia, a small island of the Caribbean nation of St. Vincent and the Grenadines. The area is in the West Indies breeding ground, so whales taken here could be from any of the North Atlantic feeding grounds. The IWC has established a block quota of 24 for the period 2013 – 2018 under the Aboriginal Subsistence Whaling management program (IWC 2015). The whales are hunted using a rowing boat and a hand-thrown harpoon with the line attached to the boat. The whale is killed using a shoulder gun firing an explosive grenade, or using hand lances (Adams 1971). The whale is then towed to shore for processing; today motorboats are sometimes used to assist in this process. The whale is processed on shore and the meat and oil are distributed, bartered or sold on Bequia or neighbouring islands within St Vincent and the Grenadines. No export is permitted.

Whaling in Greenland

Whaling in West Greenland has a very long history. The Thule Inuit, who occupied Greenland beginning around the year 1000, were skilled marine hunters who hunted several species of cetaceans, including the humpback whale. They used the kajaq (kayak) and the larger umiaq skin boats to pursue whales on the open seas. Whales were struck with hand-thrown, detachable head harpoons, with lines attached to skin floats. Hunters often wore the atallaaq, a drysuit made of waterproof seal skin, in which they would actually jump onto the whale to deliver the lethal lance strikes (Greenland 2012). Contact with American and European bowhead whalers began in the 18th century, and Greenlandic Inuit were quick to adopt some of their equipment and techniques, including faster wooden boats, metal-edged harpoons, lances and flensing tools, and hempen ropes.

Whaling in Greenland. © Fernando Ugarte

Whaling in Greenland. © Fernando Ugarte

By the beginning of the 20th century, commercial whalers had reduced populations of bowhead and humpback whales in Greenlandic waters to the point that whaling from small boats was no longer feasible. As a result, most hunting for large whales in the middle part of the century was carried out by one catcher vessel operated by the Royal Greenland Trading Company, the Sonja. This vessel operated from 1924 to 1958, with a brief cessation during the Second World War. The Sonja was steam-powered vessel that used mechanized whaling methods, including a harpoon cannon and explosive grenades. Whales were towed to villages on the Greenland west coast, where they were flensed by local people in return for a portion of the catch. This provided a welcome and needed source of food for the people of Greenland. Most of the catch consisted of fin and blue whales, but some humpback whales were taken (Caulfield 1997).

Beginning in the 1940’s, some Greenlanders began to equip their fishing vessels with harpoon cannons to participate in seasonal whaling. Minke whales were the main target of this hunt, but some fin, blue and humpback whales were also taken (Caulfield 1997, Greenland 2012). These vessels generally distributed their catch locally or sold it to neighbouring villages or larger centers.

In 1955, the IWC imposed a quota of 10 humpback whales per year on West Greenland; this was reduced to 9 in 1984 and 8 in 1985. Whaling for humpbacks was prohibited in 1986 as there was concern that the stock had been depleted. In 2007, Greenland requested a quota for humpback whales under the Aboriginal Subsistence Whaling management program at IWC, and in 2010, Greenland implemented a catch quota of 9 humpback whales per year for West Greenland, with the possibility of carrying over up to two unused quota animals from one year to the next (Greenland 2012).

Modern whaling in Greenland

Recent quotas and catches of humpback whales in Greenland. Data from the National Progress Reports.

Whaling for humpback whales resumed in Greenland in 2010 after a cessation of 30 years. However during this period, Greenlandic whalers continued to take minke and fin whales, so the skills of whaling were not lost. Whaling for large whales in Greenland is done using fishing vessels equipped with harpoon cannons and other equipment necessary for whaling. Only the largest vessels, over 36 feet in length, can participate in the hunt for humpback whales.

The primary weapon used is the 50 mm Kongsberg harpoon cannon. This fires a harpoon with a rope attached into the whale. As the harpoon enters the whale, a hook triggers the firing of a “Whale Grenade 99” loaded with 30 – 45 g of penthrite explosive into the whale. A timed fuse detonates the grenade, killing or severely injuring the whale through concussion and tissue damage. Gunners generally target the heart and lung area by aiming for the area close to the pectoral fins (NAMMCO 2010, 2015).

Since the resumption of humpback whaling in 2010, median Time to Death (TTD) for humpback whales in the Greenlandic hunt has ranged from 7 minutes in 2010 to 15 minutes in 2013. The percentage of whales that die instantaneously after being hit has ranged from 17% in 2010, 2013 and 2014 to 50% in 2011. These values are similar to those for fin whales which are hunted using similar methods (NAMMCO 2015). Struck and lost is generally low, ranging from 0% in most years to a high of 43% in 2012. In recent years, NAMMCO has held two Expert Group meetings on reducing TTD in whale hunts (NAMMCO 2010, 2015). In addition, NAMMCO has developed a Hunting Manual for baleen whales, available free of charge online in English, Norwegian and Greenlandic (NAMMCO 2014).

Once the whale is secured, it is towed to shore to suitable butchering area at the next high tide, and the whale is flensed at low tide. The meat is shared amongst the participants in the hunt, or sold at local markets, particularly the open-air markets (Greenlandic Kalaalimineerniarfik, Danish brædtet­) but also to supermarkets, hotels and restaurants.  Operating a whaler equipped with a harpoon cannon can be very expensive: the cannon alone might cost US $60,000 and each grenade costs as much as US $1,500 (Greenland 2012), and fuel is very expensive in Greenland. Therefore, whalers require some monetary return in order to continue whaling. No export of whale products from Greenland is permitted.

Other Human Impacts

Whale watching

Humpback whales are prime targets for whale watching because they have a coastal distribution accessible to shore-based operators, exhibit spectacular surface behaviour and are relatively easy to approach. Whale watching has experienced spectacular growth worldwide in the past few decades, with commercial operations springing up in areas where whales can be accessed within a reasonable distance from the coast. The whale watching industry was estimated to have a worldwide value of over 2.5 billion US dollars in 2009 (O’Connor et al. 2009).

Humpback whale and whale watching boat © M. Acquarone

Humpback whale and whale watching boat © M. Acquarone

Commercial whale watching operations that specialize on humpbacks operate in Norway, Iceland, West Greenland and other North Atlantic nations. In Iceland, the whale watching industry has grown explosively in recent years, and had a value of nearly 17 million US dollars annually in 2008 with over 120,000 participants (O’Connor et al. 2009, Martin 2012). Other benefits include employment, public education and assistance in research and monitoring programs.

While usually considered a relatively benign and sustainable “use” of marine mammals, whale watching can have short-term impacts on individuals or groups of whales which, if experienced frequently, can lead to population level effects. Humpback whales may react to vessel noise and/or the simple proximity of vessels in a number of ways. The most frequently observed reaction is an increase in swimming speed when boats are nearby (Boye et al. 2010, Bettridge et al. 2015). There may also be an increase in surface behaviours, and a tendency to move away from vessels, although the opposite effect is sometimes observed (Magnúsdóttir 2011, Martin 2012, Bettridge et al. 2015).

The long-term effects of high-intensity whale watching on humpback whale populations are not well known, but appear to be slight. Humpback whale populations have continued to grow in the North Atlantic despite massive increases in whale watching activity in many areas. Weinrich and Corbelli (2009) monitored individual humpback whales exposed to different levels of whale watching activity, and found no detectable effects on calf production or survival. However such effects are notoriously difficult to detect, and may require studies lasting at least the generation time of the species.

The potential negative effects of whale watching can be mitigated with suitable regulation or voluntary codes of conduct among whale watching operations. Such regulation generally includes a speed limit when approaching a group of whales, a close approach distance limit, and a requirement to stop if the vessel is approached by whales (Martin 2012). To date, NAMMCO member countries have used industry codes of conduct to regulate whale watching. The efficacy of or compliance with these codes have not been assessed.

Whale watching specializing in humpback whales has become popular in the Nuuk Fiord system of West Greenland. Most of the whales that use this area do so for a few weeks each summer, and return year after year. This leads to a potential conflict between whale hunting and whale watching, as the removal of the few “resident” whales could have an adverse effect on the local whale watching industry (Boye et al. 2010).

By-catch and entanglement

Among large whales, humpbacks seem particularly prone to becoming entangled in fishing gear. They consume pelagic fish that are also sought by fisherman, and are often found in coastal areas with intense fishing activity. A large proportion of some stocks may become entangled at some point in their lives: in the Gulf of Maine, between 48% and 65% of humpback whales have scars that likely resulted from gear entanglement (IWC 2002). Yearling whales are more prone to entanglement than older ones, but whales of all ages become entangled. While clearly many whales survive entanglement events, some do not, and a large proportion of dead-stranded humpback whales show evidence of entanglement in some areas (Henry et al. 2014). Mark-recapture studies have shown that juveniles are less likely than adults to survive gear entanglements, and that death due to entanglement may account for 3 -4% of total mortality in the Gulf of Maine (Bettridge et al. 2015). Females that showed signs of entanglement injury produced fewer calves than those that did not (IWC 2002), so there may be population-level effects in addition to direct mortality.

© NOAA

Humpback whales are particularly vulnerable to static gear such as gill nets and lobster and crab pots, becoming entangled in the buoy or groundlines (Johnson et al. 2005). For example, the rate of entanglement off Newfoundland dropped from 64 per year to 19 per year after the moratorium on the inshore cod fishery was introduced in 1992 (IWC 2013). In some areas, rescue and release programs have been successful in freeing a high percentage of entangled whales (IWC 2002), but many entangled whales are presumably unobserved. Changes in gear type, such as reducing the use of static gear in areas of high whale density, or including “weak links” in buoy and float lines, may also be effective in reducing death or injury due to entanglement.

Vessel strikes

Humpback whales are second only to fin whales in the frequency of reported vessel strikes (Bettridge et al. 2015). Ship strikes may be the cause death in 30% or more among dead stranded humpback whales on the US eastern seaboard (Henry et al. 2014, Laist et al. 2001). Most lethal ship strikes are by ships greater than 80 m in length travelling at a speed in excess of 14 knots (Laist et al. 2001). Experimental studies have shown that strike rates drop by over 90% if ship speed is reduced below 12.5 knots (IWC 2016). An obvious mitigation measure is therefore to reduce ship speed in areas of high whale density.

Climate change

Whales may respond to a changing climate in at least three different ways: by redistribution, i.e. changing their seasonal migratory pattern; by adaptation to the change, or by extinction. Humpback whales as a species have shown large historical changes in distribution in the North Atlantic, so it seems likely that they will continue to respond to a changing environment by redistribution, to the extent that this is possible for them (Bettridge et al. 2015). A warming climate may in fact open up more of the ice-free boreal habitat favoured by humpback whales as feeding ground than is presently available for them.

There is already evidence that climate-induced changes in humpback whale behaviour are occurring. Higdon and Ferguson (2011) found that humpback whales were being sighted in areas of the Canadian Eastern Arctic where they had never been seen before, and postulated that a reduction in summer ice cover in Hudson Strait had allowed the whales to penetrate into the area. Ramp et al. (2015) found that humpback whales were arriving at the Gulf of St. Lawrence feeding ground about four weeks earlier in 2010 than they did in 1987, corresponding to a change in arrival date of about one day per year. They were also departing earlier by a similar length of time. This change was most closely correlated to a rise in sea surface temperature over the period, which also corresponded to an earlier ice-free date.

While the effects of climate change on humpback whales cannot be predicted, it is likely that continued warming and a reduction in Arctic ice cover will result in a northward shift in summer distribution in some areas, and possible changes in seasonal occupation in others. Climate change is likely less of a danger to the adaptable humpback whale than to some Arctic, ice dependent species, for which the total amount of habitat is being reduced.

Acoustic pollution

Humpback whales produce a wide variety of sounds which they use for communication and possibly also to locate prey or otherwise sense their environment. Noise resulting from shipping, seismic exploration, and military or other sonar can affect humpback whales by masking their sounds and reducing their effective range. The ocean is rapidly becoming a more noisy environment: anthropogenic sound production in coastal areas is thought to have doubled each decade for the last 30 years (Bettridge et al. 2015).

Humpback whales may respond to increased background noise by increasing the length of their songs, or by becoming quieter (Bettridge et al. 2015). In contrast Gong et al. (2015) found no changes in humpback vocalizations associated with military sonar in the Gulf of Maine.

Acoustic interference with humpback whales can be mitigated by reducing or eliminating seismic and sonar activities in areas and seasons when whales are present in high densities, especially during the mating season when singing whales are present.

Contaminants

As long-lived top level marine predators, humpback whales tend to accumulate organic pollutants such as pesticides in their blubber. These pollutants can also be transferred from mother to calf through lactation (Bettridge et al. 2015). Known consequences of such bioaccumulation of organic contaminants in marine mammals include impaired immunity and increased susceptibility to disease, neurotoxicity and reproductive impairment (Elfes et al. 2010). However concentrations in humpback whale tissue are generally below those known to cause such impairments in other animals (Ryan et al. 2013). Concentrations do vary greatly between whales sampled in different areas, probably reflecting the extent of contamination in humpback whale prey. For example concentrations of organic contaminants were much lower in whales sampled around the Cape Verde Islands than in those sampled in the Gulf of St Lawrence of Gulf of Maine, perhaps reflecting agricultural inputs in the latter areas (Ryan et al. 2013).

Some types of algal blooms produce toxins harmful to marine mammals, and these blooms have been associated with inflow of untreated industrial and domestic wastewater. Toxins associated with an algal bloom killed at least 14 humpback whales in 1987-88 off the US eastern seaboard, and such toxins are often found in the tissues of dead stranded whales (Bettridge et al. 2015). However the population level effects of these toxins are not known.

Research in NAMMCO Member Countries

All NAMMCO member countries as well as Canada have participated in the North Atlantic Sightings Surveys, and the humpback whale has been a target species in all areas. These surveys are coordinated through the Scientific Committee of NAMMCO. In addition each country conducts other important research on the biology and ecology of humpback whales.

Summer sightings of humpback whales during all NASS from 1987-2015. Black lines indicate areas surveyed (not all areas surveyed in each year).

Iceland

The Marine Research Institute (MRI) is the Icelandic governmental body responsible for research concerning conservation and management of cetaceans in Icelandic waters. The MRI’s main research activities on humpback whales in recent decades have focused on: 1) Distribution and abundance, primarily through participation in large scale international surveys but also using data from opportunistic platforms such as fish- or oceanographic research cruises and commercial whaling and whale watching platforms; 2) Photo-identification studies. The MRI participated in the YoNAH project in the early 1990‘s and has continued photo-id studies ever since, including the maintenance of the Icelandic central photo-identification database. 3) Genetics. Samples obtained from biopsies (including YoNAH) as well as from stranded or bycaught animals have been used in international population genetic studies. 4) Satellite telemetry. Since the late 1990‘s the MRI has experimented with satellite telemetry on several cetacean species including humpback whales. 5) Strandings and net entanglements. The MRI is responsible for monitoring strandings and bycatches of cetaceans in Icelandic waters.

Iceland has developed a Whale Photo Identification database that allows cataloging of photographs and photo-matching to identify re-sightings. While several species are included, the humpback whale has been the main focus of photo-ID work. To date, the catalogue contains over 1,100 photographs of humpback whales, of which 722 are of unique individuals. Most of these are from Iceland, but animals from Norwegian and Irish waters are also included. Of these, 130 have been sighted two or more times, providing information about site fidelity, migration, stock identity and life history. In addition to the photo collection, biopsy samples for genetic and other analyses have been collected from more than 70 humpback whales in Icelandic waters.

Greenland

As one of only two countries in the North Atlantic that continues to hunt humpback whales, Greenland has participated in the NASS surveys, using aerial surveys to cover the west coast of Greenland from Cape Farewell north to about 70°. In 2015 the east coast of Greenland was also covered, which revealed relatively large numbers of humpback whales in that area. This may mean that these waters constitute a feeding area for humpback whales, at least in some years. Greenland has also contributed fluke photographs and genetic samples to international humpback whale database, and participated in the YoNAH and follow-up projects.

Greenland has been very active in tracking whales using satellite tags. This has led to a greater understanding of the local and migratory movements of humpback whales (Heide-Jørgensen and Laidre 2007). In addition, short term tagging efforts have advanced our knowledge of the kinematics of lunge feeding by humpback whales (Simon et al. 2012).

As a whaling nation, Greenland monitors its whale hunts and participates in efforts to improve hunting methods and reduce time-to-death and struck and lost rates in whale hunts (NAMMCO 2010, 2015). Since the resumption of humpback whaling in 2010, median Time to Death (TTD) for humpback whales in the Greenlandic hunt has ranged from 7 minutes in 2010 to 15 minutes in 2013. The percentage of whales that die instantaneously after being hit has ranged from 17% in 2010, 2013 and 2014 to 50% in 2011. These values are similar to those for fin whales which are hunted using similar methods (NAMMCO 2015).

Whale-watching has become a valuable part of the tourist industry in Greenland, particularly in the fiord system surrounding the capital city, Nuuk. Research in this area has focussed on quantifying the effect of close approaches of whale watching vessels on humpback whale behaviour. The most frequently observed reaction is an increase in swimming speed when boats are nearby (Boye et al. 2010). The humpback whales that use this area tend to return there year after year, leading to the suggestion that hunters should avoid taking these whales to support the whale watching industry.

Norway

Norway surveys a huge area of the Barents, Norwegian and North Seas on a six-year rotation, covering a part of the area each year. While minke whales are the primary target species of the survey, all species including humpback whales are counted. Norway also contributes fluke photographs and genetic samples to international humpback whale database, and participated in the YoNAH and follow-up projects.

A major focus of Norwegian research has been to understand the ecological relationships between baleen whales, pelagic fish such as capelin and Arctic cod, and their invertebrate prey, krill and pelagic amphipods. A series of surveys conducted jointly with Russia in the Barents Sea south of Svalbard between 2003 and 2007 collected simultaneous data on the abundance of krill, amphipods, pelagic fish and cetaceans (Skern-Mauritzen 2011). Baleen whales including humpbacks were found at highest density in a narrow arc along the north edge of the polar front, which corresponded closely to the highest densities of krill in the area. While this suggests that humpback whales graze primarily on krill in this area, the abundance of capelin was at a low level during most of this period. Future work will address how the distribution of cetaceans responds as ecosystem conditions change.

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