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Species at Risk Act - Legal Listing Consultation Workbook, Fin whale (Atlantic Population)
Information on Fin Whale
Status: Species of special concern.
Last COSEWIC assessment: May 2005.
2.1. Distribution and migration of fin whale
Fin whale is a deep-water cetacean that can be found in every ocean of the world. However, it is more abundant at temperate and polar latitudes. It can be encountered in coastal waters but occurs most often in the open sea. It seems to be absent in most equatorial areas or floe edges. Northern hemisphere fin whales (Balaenoptera physalus physalus) and those from the southern hemisphere (B. p. quoyi) are likely geographically isolated sub-species, and are distinct at the reproductive level as well. Morphological differences distinguish them. Two distinct populations can be found in Canadian waters, one in the Pacific and the other in the Atlantic.
Fin whale is a migrating species that spends the summer in the northern waters rich in food between Baffin Bay, in Canada, and Cape Hatteras in North Carolina. The winter distribution range of fin whale is not well known. It travelled the waters between the coast and the continental shelf of the Newfoundland Grand Banks all the way down to the Gulf of Mexico. Generally, their summering area is not as spread out as their wintering area. Still, the distribution range limits of this cetacean throughout the year are not well documented.
In the Canadian Atlantic, different summering aggregations are spread out in the Estuary and Gulf of St. Lawrence, the Bay of Fundy, the costal and offshore waters of Newfoundland, off the coast of Labrador up to Davis Strait, and on the Scotian Shelf. During the summering period, from June to the fall, the fin whale is the most commonly seen large whale in the Bay of Fundy and on the Scotian Shelf. It seems that the Newfoundland and Nova Scotia stocks migrate south in winter, with the Newfoundland stock occupying the area vacated by the Nova Scotia stock, which migrates further south. In winter, certain individuals stay along the Atlantic coast of Nova Scotia.
In the Estuary of St. Lawrence, near Tadoussac, 88 individuals were photo identified by a team of scientists between 1986 and 2001. Of this number, approximately 30% are considered seasonal residents because they have been seen almost every year. The rest of them are considered regular or occasional visitors. Downstream, along the northern coast of the Gulf of St. Lawrence, over 300 fin whales were photo identified since the early 1980s.
2.2. Biology and behaviour of fin whale
Second largest cetacean in the world after the blue whale, the Atlantic fin whale is smaller than its congeners in the southern hemisphere and reaches an average length of 24 m, with an average weight between 40 and 50 tons. Females are usually larger than males. They have slender and hydrodynamic bodies, allowing them to swim at great speeds. Their backs are dark grey to brownish grey, and their stomachs white. Fin whale is different from other species because of the nonsymmetric colouration of its lower jaw (darker on the left side) and baleens (yellowish band on the right side, in front, and the rest a greyish blue).
For the fin whale, sexual maturity is usually reached at about 6-7 years of age for females and 7-8 years of age for males (for an average length of 17.2 m). Breeding and calving appear to occur in the winter in lower latitudes. Females give birth to a single calf (of approximately 6 m) after an 11 or 12-month gestation period, and weaning occurs 6-7 months later. The interval between two births is estimated at about 2½years. The fin whale population could reproduce at an annual rate of 8 calves per 100 adult females. However, the survival rate of calves and juveniles is still mostly unknown.
2.2.3. Social behaviour and relationships among species
The bond between the mother and her young appears to end during the weaning period, and there doesn’t seem to be any lasting bond between individuals of a same population. However, there have been animals that have created temporary associations especially during movements (2-7 individuals) and at feeding sites (2 or more).
Distribution ranges and a common diet bring together different species of baleen whales. It is not rare to come across groups made up of large whales (blue and fin), and a certain number of hybrid individuals have been identified in the Northern Atlantic, particularly in Iceland. In overlapping areas, it is likely that this species shares the same food resources as other whale species. For example, there could be competition between humpback and fin whales in feeding areas harbouring schools of capelin, if this resource was limited.
The variety in the fin whale diet is as much a question of prey availability as it is a question of preference. This flexible dietary strategy allows the animal to change target if one particular prey diminishes. In a similar situation, a stenophagous species (restricted diet) such as the blue whale is clearly at a disadvantage. In the Northern Atlantic, the main prey for fin whales is small invertebrates, schools of fish and squid. In Canadian waters, they mostly feed on krill, capelin, and in a lesser degree, on Atlantic herring. Fin whales that are found in the St. Lawrence Estuary would benefit from the great concentration of krill and capelin found at the mouth of the Saguenay River. Capelin appear to be the main prey for fin whales found off the coast of Newfoundland, while those found in the Bay of Fundy feed mainly on krill. Fin whales have been seen feeding on herring off the coast of Nova Scotia.
According to the SARA definition, a “habitat” could include: calving, rearing and feeding areas, as well as migration routes on which the species’ survival depends, during the annual cycle and for each age and gender class. Unfortunately, the fin whale data collected so far focuses more on summer nursing areas than on wintering areas.
If fin whales travel a lot in coastal waters during the summer, some individuals could reach open water and the south in winter. The geographic distribution of fin whales suggests a preference, during summer, for areas where surface water temperature is cooler such as in the Bay of Fundy and for upwelling areas. Along the coasts, they feed on sites with rich concentrations of prey, such as at the head of the Laurentian Channel (St. Lawrence Estuary). Eastern Nova Scotia would have enough food to feed fin whales during the entire year.
It is difficult to describe changes to a habitat (drop in productivity, increased competition, etc.) for an aquatic, migrating and pelagic species like the fin whale. This animal appears to possess the physical capacity to travel great distances in order to find adequate parcels. Factors that are likely to change the habitat area have probably more to do with changes in productivity on a more global scale. The quality and size of the habitat also depend on interactions between the species, its prey and its competitors.
The fin whale vocalizes a lot. It emits low frequency sounds that can travel hundreds, even thousands of kilometres. Vocalization could be used to announce southward migration in the fall, and northern migration at the end of winter. Individuals found on the Scotian Shelf emit louder songs towards the end of August, all through fall and in the middle of winter. In the North Pacific, signals (20 Hz) used by fin whales are linked to male reproductive behaviour. It is possible that fin whales use earth’s magnetic field to find their way during migration.
2.3. Why has COSEWIC given the Fin Whale “special concern” status?
Here is the reason for the fin whale status designation by COSEWIC:
As of the late 19th century, whaling techniques improved and enabled the capture of fin whales (a very fast species whose body sinks after death). For almost a century, stocks were over-exploited and therefore dangerously reduced. The abundance of these whales was not measured until the beginning of the whaling industry. However, we do know that more than 13,337 fin whales were killed near Newfoundland and Labrador between 1903 and 1945, and that the Nova Scotia stock felt the pressure from whaling between 1964 and 1971. The most reliable and recent assessment is from 1999 and estimated that 2,814 individuals could be found between Georges Bank (N.S.) and the mouth of the Gulf of St. Lawrence, and 380 individuals inside the Gulf. Even though whaling activities have been interrupted in Canada since 1971, several man-made threats are potentially harmful for fin whales.
2.4. What are the threats to the fin whale?
A degradation of the habitat caused by a drop in prey availability, and a decline in fitness brought on by chemical pollution enters into the category of limiting factors, while accidental catches, collisions and noise disturbance represent threats. Studies are nonetheless necessary in order to properly define and understand the impact of these elements on the recovery and sustainability of the species.
2.4.1. Limiting factors
Reductions in prey abundance
The habitat of large whales is intimately linked to prey distribution. Any reduction in a prey’s availability can consequently be perceived as a reduction in habitat. The phenomenons that can lead directly or indirectly to a reduction in prey are climatic changes, interspecific competition and commercial fishing.
There apparently isn’t any proof that baleen whales suffer from the toxic effects of metal or organochlorine contamination of their environment. However, other marine mammals appear to be affected by immunotoxic chemical products. The known effects of these pollutants on animals are: a reduction or change to the immune response, reproductive disorders, lesions and cancers. The organochlorine contamination rate of certain fin whales in the Gulf of St. Lawrence is nonetheless high enough to generate some concern but lower than levels recorded 20 years earlier. The contamination rate could vary according to the geographic area.
Entanglement in fishing gear
After whaling, which is now forbidden in Canadian waters, entanglement in fishing gear appears to be the most significant threat for fin whales. However, it is difficult to evaluate the consequences because, first of all, the number of accidental catches seems to be underestimated either because they aren’t being reported or because the individual couldn’t be identified or was never found. Secondly, fin whales appear to be less susceptible to entanglement than their congeners (blue whale, mink whale) because of their smaller appendage and their strength. Finally, because fin whales don’t expose their bodies as much during their dives, net or cable marks often remain hidden from the observer. Some cases of fin whale entanglement have been reported and some were even fatal. More than on the Pacific coast, the population of eastern Canada has seen its distribution range cross over fishery areas, which increases the risks.
Collisions with vessels
Fin whales are the most common victims of collisions with long and fast commercial ships. Many ships have been sighted with a carcass on their bow. Collisions are not all fatal but the numbers are likely underestimated because the bodies of these whales usually sink when they die. It is estimated that 4% of living individuals that have been photo identified have marks from accidents with ships. Because they are accustomed to the noise produced by these ships in heavy traffic areas, their vigilance might be somewhat reduced and this may cause accidents. Heavier traffic as well as the increase of ship sizes represents an additional threat for fin whales. This would be the case in the St. Lawrence Seaway, which is the main access way for commercial fleets on the east coast of North America and in the area of the port of Halifax.
Ambient noise levels in the ocean have increased significantly globally over the past century. Noise produced by commercial vessels, detonations from seismic exploration, and all other low frequency noise are likely to produce behavioural and physical changes in fin whales. The distance between the noise source and the animal, the emission frequency, the intensity and duration of the noise, the recurrence of noisy events, and the whale’s hearing ability and degree of habituation are all factors that interact and determine the extent of the impact.
In response to certain noises, whales can interrupt their feeding and mating activities, divert their route, or abandon a critical habitat. Recurring sounds, even at low intensities, could produce chronic stress and have long-term health impacts on individuals. In the case of very loud noises, or when the noise source is close, the animal could experience reduced hearing sensitivity or hearing loss. Manmade noise can also overshadow (mask) sounds that fin whales need to hear to breed, feed, or navigate.
Seismic exploration and oil and gas development
Sounds emitted by seismic exploration and oil and gas development, in addition to being responsible for physical harm, would cause fin whales to avoid these areas and interrupt their dives (the noise level being lower near the surface). The impact of this type of development raises a number of questions, particularly when it comes to sound travelling over great distances in underwater environments. The issue concerns mostly fin whale populations because of potentially high hydrocarbon sectors spilling over areas harbouring heavy concentrations of the species.
Although it has been interrupted in Canada, whaling continues in the North Atlantic, notably in Greenland (subsistence harvest) and eventually in Iceland (which is interested in resuming this activity).
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