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Fin whale

Fin whales (Balaenoptera physalus) are widely distributed in the world’s oceans [1]. Populations in the North Atlantic, North Pacific and southern oceans probably mix rarely, if at all. Within particular oceans, populations have been determined to belong to regional stocks. The Marine Mammal Protection Act recognizes three stocks of fin whales in the North Pacific: 1) the California/Oregon/ Washington stock, 2) the Hawaii stock, and 3) the Alaska stock [2]. A western North Atlantic stock inhabits U.S. waters along northeastern coasts [3]. Fin whale populations exhibit differing degrees of mobility, presumably depending on the stability of access to sufficient prey resources through the year [1]. Most groups are thought to migrate seasonally, in some cases over large distances [1]. They feed at high latitudes in summer and move to low latitudes in winter. Some groups apparently move over shorter distances and can be considered resident to areas with a year-round supply of adequate prey.

Fin whales were hunted, often intensively, in all the world's oceans for the first three-quarters of the 20th century [1]. From 1947 to 1987, approximately 46,000 fin whales were taken from the North Pacific alone [2]. Commercial whaling did not end until 1976 in the North Pacific and 1987 in the North Atlantic. The current status of fin whale populations relative to pre-whaling levels is uncertain.

In the North Pacific, pre-whaling populations were estimated to be between 42,000 and 45,000 [2]. By 1973, the North Pacific population is thought to have been reduced to between 13,620 and 18,680 -- less than 38% of historic carrying capacity [2]. More recently, however, there is some indication that the population may be growing. The California/Oregon/Washington stock of the North Pacific is thought to be increasing [5]. Fin whale acoustic signals are detected year-round off northern California, Oregon and Washington, with a concentration of vocal activity between September and February [2]. Fin whales increased in abundance along the California coast between 1979 and 1996, and based on ship surveys in 2001, they continued to increase. Populations appeared to be increasing monotonically from 1991 to 2001 [5]. In 2001, 3,279 (CV= 0.31) were estimated in California, Oregon and Washington coastal waters [2].

Since 1999, information on abundance of fin whales in Alaskan waters has improved, however, and although the full range of fin whales in these areas has not yet been surveyed, a rough estimate of the size of the population west of the Kenai Peninsula is 5,703 [6]. Surveys conducted in 1999 and 2000 in the central-eastern Bering Sea and southeastern Bering Sea provided provisional estimates of 3,368 (CV = 0.29) and 683 (CV = 0.32), respectively [6]. One aggregation of fin whales spotted in 1999 involved more than 100 animals [6]. Because historical abundance information is lacking, population trends are difficult to determine [6].

Fin whales are rare in Hawaiian waters and the stock is thought to be quite small [7]. Over the course of 12 aerial surveys conducted within about 25 nmi of the main Hawaiian Islands in 1993-98, only one fin whale was sighted [7]. More recent acoustic data suggest that fin whales migrate into Hawaiian waters mainly in fall and winter [7]. In 2002, a ship survey of the entire Hawaiian Islands resulted in an abundance estimate of 174 (CV=0.72) fin whales [7].

Western North Atlantic fin whales off the eastern U.S. coast north to Nova Scotia and the southeastern coast of Newfoundland are considered a single stock [3]. New England waters represent a major feeding ground and calving is thought to take place along mid-Atlantic U.S. latitudes from October to January. The locations used for calving, mating and wintering for most of the population remains unknown. It is likely that fin whales occurring in the U.S. Atlantic undergo migrations into Canadian waters, open-ocean areas, and perhaps even subtropical or tropical regions. An abundance of 2,200 (CV=0.24) fin whales was estimated from a 1995 line-transect sighting survey that covered waters from Virginia to the mouth of the Gulf of St. Lawrence. A more recent estimate of 2,814 (CV=0.21) fin whales, currently considered the best estimate for the western North Atlantic stock, was derived from a 1999 line-transect sighting covering waters from Georges Bank to the mouth of the Gulf of St. Lawrence [3]. Although there is little data on population trends, the minimum population estimate reported in NOAA Fisheries Stock Assessment Reports has steadily increased since 1992.

The main direct threat to fin whales today is the possibility of illegal whaling or a resumption of legal whaling [1]. In 2006, Japan announced that it will expand hunts to include fin whales [4]. They expect to harvest 10 fin whales from Antarctic waters [4]. Collisions with vessels, entanglement in fishing gear, reduced prey abundance due to over-fishing and habitat degradation, as well as disturbance from low frequency noise, are also potential threats [1]. The offshore drift gillnet fishery is the main fishery likely to take fin whales [2].

[1] National Marine Fisheries Service. 1998. Draft Recovery Plan for the Fin Whale (Balaenoptera physalus) and Sei Whale (Balaenoptera Borealis). Silver Spring, MD.
[2] NOAA Fisheries. 2005. Stock Assessment Report. North Atlantic Right Whale (Eubalaena glacialis): Western Stock revised Dec., 2004. National Oceanic and Atmospheric Administration, Washington, D.C.
[3] NOAA Fisheries. 2004. Stock Assessment Report. Fin Whale (Balaenoptera physalus): Western North Atlantic stock. Revised Dec. 2004. National Oceanic and Atmospheric Administration, Washington, D.C.
[4] Hans Greimel, Associated Press. 2005. Japan To Double Usual Whale Kill in New Antarctic Hunt, Expanded To Include Fin Whales. Nov. 9, 2005.
[5] Barlow, J. 2003. Preliminary Estimates of the Abundance of Cetaceans along the U.S. West Coast: 1991-2001 Southwest Fisheries Science Center Administrative Report LJ-03-03. Accessed at (http://swfsc.nmfs.noaa.gov/prd/PROGRAMS/CMMP/default.htm).
[6] NOAA Fisheries. 2004. Stock Assessment Report. Fin Whale (Balaenoptera physalus): Northeast Pacific stock. Revised 10/21/2004.
[7] NOAA Fisheries. 2005. Stock Assessment Report. Fin Whale (Balaenoptera physalus): Hawaiian stock. Revised 3/15/2005.

Banner photo © Phillip Colla