Finback Whale

Balaenoptera physalus

Description

The slender, elongated finback whale, Balaenoptera physalus, reaches lengths of up to 88 ft (27 m) and weights of over 60 tons (54 metric tons), making it the world's second largest mammal after the blue whale. It has 70-80 throat furrows, a flat, V-shaped head, and a short, sharply pointed dorsal fin. Coloration is a uniform dark gray above and white beneath. The right lower portion of the head and right jaw are always white.

This species is also known commonly as the fin whale, common rorqual, finner, or razorback.

Behavior

The swift finback whale migrates in groups, called pods, numbering from a few individuals to as many as several hundred. The finback feeds in cooler, subpolar waters during the summer, then it moves south into temperate waters for calving in winter. The finback has a more varied diet than the blue whale, consisting of plankton, crustaceans, and small fish. North Pacific finbacks feed primarily on herring, capelin, and crustaceans, while krill (tiny shrimp-like crustaceans) make up the bulk of the Antarctic finback diet.

Finbacks breed in fall and winter, and the gestation period is between 11 and 12 months. Females typically bear a single calf, which weighs nearly 2 tons (1.8 metric tons) at birth. Calves are nursed for seven months and are fully grown in seven years. The life span of these mammals may be from 40 to 100 years.

When the finback breaks water, it spouts 20 ft (6 m) with a shrill whistling sound, sending water vapor forward in an elliptical arch. Underwater, it makes a loud, low-frequency moan that is near the lower limits of human hearing.

Habitat

The pelagic finback is widely dispersed throughout the world's oceans.

Distribution

The finback whale is found in greater concentrations in the southern hemisphere than in the northern. Because it is able to attain a swimming speed of over 20 mph (32 kph), the finback eluded two centuries of whaling. Only with the advent of power boats in the first part of this century, were whalers able to take finbacks in large quantities. By the 1950s, whalers had killed over 250,000 of these whales. As recently as the mid-to late-1980s, the total population was thought to be over 200,000, but this has been revised downward.

Several stocks of finbacks are recognized in the Greenland and Norwegian seas, the North Pacific and Arctic oceans, and the temperate and circumpolar waters of the southern hemisphere. Scientists now believe that fewer than 100,000 of these mammals survive. Findings of a ten-year survey conducted by the International Whaling Commission (IWC), released in 1989, counted only about 4,100 finbacks in prime Antarctic waters. While not all finbacks use these waters, the surprisingly low figure has caused concern in the scientific community.

Threats

Perhaps less in danger than some other whales, the finback whale has nevertheless suffered from commercial whaling and numbers have rebounded only slightly (if at all) since most whaling was stopped by international treaty.

The finback is a fast swimmer and sinks when killed, making it difficult for whalers to successfully exploit this species. It was not until steam powered pursuit boats and the explosive harpoon were introduced to Norway in 1864 that the species experienced serious threat.

Conservation and Recovery

The taking of whales worldwide is administered by the IWC, which sets quotas for member counties. In 1986, members voted a complete moratorium on whaling in preparation for phasing it out entirely. The agency unfortunately has no statutory authority nor any means of enforcing the whaling ban, other than the pressure of public opinion. Several countries, including Japan, Iceland, and the Republic of Korea, continue to take whales for "scientific purposes," exploiting a loophole in the international treaty. Japan remains the largest market for products derived from whales.

Contacts

Office of Protected Species
National Marine Fisheries Service
1315 East-West Highway
Silver Spring, Maryland 20910

U.S. Fish and Wildlife Services
Department of Endangered Species
Mail Stop 420ARLSQ
1849 C St., NW, Washington, D.C. 20240

References

Baker, M. L. 1987. Whales, Dolphins, and Porpoises of the World. Doubleday, Garden City.

Evans, P. G. 1987. The Natural History of Whales and Dolphins. Facts on File Publications, New York.

Hoyt, E. 1984. The Whale Watcher's Handbook. Doubleday, Garden City.

Mizrock, S. A., and A. York. 1984. "Have Pregnancy Rates of Southern Hemisphere Finback Whales Increased?" Report of the International Whaling Commission Special Issue 6:401-410.