Sperm whale

Listed: 6/2/1970

Status since listing: Stable

The sperm whale (Physeter macrocephalus) occurs in all oceans worldwide and were once abundant [1]. Over the past two centuries, however, commercial whalers killed somewhere around 1 million sperm whales [1]. Despite this, sperm whale populations are larger than those of other large whale species (rough estimates put the population somewhere between 200,000 and 1.5 million) [1]. Commercial whaling of sperm whales declined in the 1970s and 1980s, and virtually ceased when the International Whaling Commission implemented a moratorium against hunting sperm whales in 1988 [1]. Although populations are expected to have increased due to the cessation of whaling, determining population trends has been difficult. This is in part because sperm whale migration patterns are not well understood (patterns seem to vary with age and sex) [1] and because sperm whales occur in larger groups and tend to range more widely, making abundance estimates more variable than those of other large whales with similar population sizes [2]. Current threats to sperm whales include anthropogenic noise, incidental ship strikes and gillnet mortality [1]. The accumulation of stable pollutants (e.g. PCBs), chlorinated pesticides (e.g. DDT), polycyclic aromatic hydrocarbons and heavy metals could also affect the health and behavior of sperm whales [1].

For stock assessment reports by NOAA, sperm whales within the Pacific U.S. are divided into three discrete areas: 1) Hawaiian waters, 2) California, Oregon and Washington waters, and 3) Alaskan waters [3]. Although there are no reliable estimates of historic sperm whale abundance in Hawaiian waters, this area was the center of a major hunting ground for sperm whales in the 19th century [3]. The current best estimate of the number of sperm whales around the Hawaiian Islands is 7,082 (CV=0.30) [3]. Because this is the first reliable estimate from surveys covering the entire Hawaiian Island area, no estimates of population trends are available [3].

In the North Pacific, the eastern North Pacific stock of sperm whales ranges into Alaskan waters [4]. In 1998, the population of this stock was estimated to be in the neighborhood of 39,000 [4]. The number of sperm whales in Alaskan waters, however, is unknown and determining population trends has not been possible [1]. It is thought that male sperm whales in particular feed in the Gulf of Alaska, Bering Sea and waters around the Aleutian Islands [1].

The population of the California, Oregon, Washington sperm whale stock has fluctuated since 1979/80 without apparent trend and appears relativelyl stable [5, 6]. Ship line-transect surveys conducted in 2001 estimated sperm whale abundance in these waters to be 1,581 (CV=0.59). This is similar to an estimate of 1,168 (CV=0.40) produced from surveys conducted between 1991 and 1993 [2]. Because of the methodologies used in early surveys, earlier population estimates are unreliable and can not be used for comparison with more recent population numbers [5].

In the Atlantic Ocean, sperm whales along the U.S. East Coast likely represent only a fraction of the total North Atlantic sperm whale stock [7]. Research indicates stable social groups, site fidelity and latitudinal range limitations in groups of North Atlantic females and juveniles, while males migrate to polar regions to feed and return to more tropical waters to breed [7]. In winter, sperm whales are concentrated east and northeast of Cape Hatteras, North Carolina [7]. In spring, the center of distribution shifts northward to Delaware and Virginia with sperm whales occurring throughout the central portion of the mid-Atlantic bight and the southern portion of Georges Bank [1]. Total numbers of sperm whales off the U.S. or Canadian Atlantic coast are unknown, although research suggests that at least several thousand sperm whales occupy these waters [7]. Ship surveys conducted along the Atlantic coast from the Gulf of St. Lawrence to Florida in 1998 resulted in a population estimate of 4,029 (CV=0.3) [7]. In 2004, the population was estimated at 3,768 (CV=0.337). Because estimates were not corrected for whale dive-time, they likely underestimated abundance. There are insufficient data to determine the population trends for this stock of sperm whales [1].

The northern Gulf of Mexico stock is present year-round in the northern part of the Gulf of Mexico, with sightings occurring most frequently in summer [1]. Recent research supports suggestions that this population represents a distinct stock [8]. A recent re-analysis of survey data collected from 1991 to 1994 resulted in a population estimate of 805 (CV=0.27) [8]. The current best estimate of this population, 1,349 (CV=0.23), is from 1996 and 2001 data that were pooled [8]. There is not sufficient data to determine population trends for this stock [8]. Of particular concern for sperm whales in the Gulf of Mexico is disturbance by anthropogenic noise from areas where oil, gas and shipping activity are high. Coastal pollution may also pose threats for this stock [8].

[1] NOAA Fisheries. Office of Protected Resources. Species Information: Sperm Whales. Website: http://www.nmfs.noaa.gov/pr/species/mammals/cetaceans/spermwhales.htm (Accessed on 12/1/05).
[2] 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. La, Jolla, CA. 31 p. [3] NOAA Fisheries. 2004. Stock Assessment Report. Sperm Whale (Physeter macrocephalus): Hawaiian Stock. Revised 03/15/2005. National Oceanic and Atmospheric Administration, Washington, D.C.
[4] NOAA Fisheries. 2003. Stock Assessment Report. Sperm Whale (Physeter macrocephalus): North Pacific Stock. Revised 5/1/03. National Oceanic and Atmospheric Administration, Washington, D.C.
[5] NOAA Fisheries. 2003. Stock Assessment Report. Sperm Whale (Physeter macrocephalus): California/Oregon/Washington Stock. Revised 12/15/03. National Oceanic and Atmospheric Administration, Washington, D.C.
[6] Barlow, J. 1994. Abundance of large whales in California coastal waters: a comparison of ship surveys in 1979/80 and in 1991. Rept. Int. Whal. Commn. 44:399-406.
[7] NOAA Fisheries. 2005. Draft Stock Assessment Report. Sperm Whale (Physeter macrocephalus): North Atlantic Stock. Revised Nov 2004. National Oceanic and Atmospheric Administration, Washington, D.C.
[8] NOAA Fisheries. 2003. Stock Assessment Report. Sperm Whale (Physeter macrocephalus): Northern Gulf of Mexico Stock. Revised Dec 2003. National Oceanic and Atmospheric Administration, Washington, D.C.