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Recovery Strategy for Blue, Fin, and Sei Whales in Pacific Canadian Waters [Proposed]

3. The Fin Whale

3.1.  Current Status

Common name:Fin whale

Scientific name:Balaenoptera physalus

Legal listing (SARA):under consideration

Assessment summary:May 2005

COSEWIC status:Threatened

Reason for designation: Currently sighted only infrequently on former whaling grounds off British Columbia. Coastal whaling took at least 7,600 animals from the population between 1905 and 1967, and thousands of additional animals were taken by pelagic whalers through the 1970s. Catch rates from coastal whaling stations declined precipitously off British Columbia in the 1960s. Based on the severe depletion and lack of sufficient time for recovery, it is inferred that present population is below 50% of its level 60-90 years ago. Individuals continue to be at risk from ship strikes and entanglement in fishing gear. (www.cosewic.gc.ca)

Occurrence in Canada: North Atlantic and North Pacific

Status history: The species was considered a single unit and designated Special Concern in April 1987. Split into two populations (Atlantic and Pacific) in May 2005. The Pacific population was designated Threatened in May 2005.

3.2.  Species Description

The fin whale is the second largest member of the family Balaenopteridae, after the blue whale. It has been characterized as the “greyhound of the sea” due to its fast swimming speed and streamlined body (Reeves et al. 2002). Fin whales are widely distributed in all the oceans of the world, in both coastal and offshore waters. Although considered a single stock in the North Pacific by the IWC, there is more likely at least an eastern and a western population (COSEWIC 2004).

Fin whales can reach 27 m (88 ft) in length, with adult females 5-10% longer than males. Adult fin whales in the southern hemisphere are up to 4 m longer than their northern hemisphere counterparts, and have longer, narrower flippers. The body is generally dark grey or brownish-grey dorsally, shading to white ventrally. Some individuals have a V-shaped chevron on the dorsal side, behind the head. Asymmetrical colouring of the lower jaw, dark on the left and light on the right, continues about a third of the distance through the baleen plates, the remainder of which are a dark blue-grey. This colouration pattern is diagnostic for the species. The ventral surfaces of the flippers and flukes are also white. Some adults show scarring indicative of lamprey or remora attachment or nicks and scars on the fins or body that may stem from interactions with fishing gear or other animals. Individual animals can be identified by means of scarring, pigmentation patterns, dorsal fin shapes and nicks (COSEWIC 2004).

The head of the fin whale is narrow, measuring about 20-25% of total body length, with the rostrum particularly pointed, prominent splash guards around the double nares (i.e., nostrils) and a single median head ridge. The eyes lie just above the corners of the mouth. The lower jaw is laterally convex and juts 10-20 cm beyond the tip of the rostrum when the mouth is shut. The dorsal fin is set about three quarters of the way back along the dorsal surface, is falcate or pointed, and can be 60 cm high. Behind the dorsal fin, the caudal peduncle has a sharp, prominent ridge (COSEWIC 2004).

Fin whales can be confused with blue, sei and Bryde’s (B. brydei) whales, and with the recently described B. omurai. However, based on the distribution of these species, confusion in Pacific Canadian waters is likely limited to blue and sei whales. The fin whale head is more pointed than that of the blue whale, with a larger dorsal fin, which is set further back and has a shallower rise than that of the sei whale. On surfacing, a fin whale’s blowholes are seen first followed by the dorsal fin. In sei whales, the blowholes and dorsal fin usually appear almost simultaneously. The blue whale is the only member of the genus Balaenoptera to regularly “fluke up” (i.e., lift its flukes above the surface when starting a deep dive) (COSEWIC 2004).

Reproduction is similar to blue whales, with females calving every 2-3 years following an 11-12 month gestation period. Calves are born at about 6 m in length, and are weaned at an average length of about 11.5 m, at 6-7 months of age. Age at sexual maturity is estimated at 5 to 15 years for both sexes, at an average length in the northern hemisphere of 17.2 m (COSEWIC 2004) . Similar to blue whales, the life span of fin whales is assumed to be around 80 years.