Observation of a male-biased sex ratio in the Gulf of St. Lawrence fin whales (Balaenoptera physalus): Temporal, geographical, or group structure segregation?

Abstract:

Knowledge about the migration, behavior, and structural organization of fin whales is limited. Although fin whales (Balaenoptera physalgs) are characterized as a migratory species, they do not seem to have a single breeding ground as found with the North Atlantic humpback whales (Megaptera novaeangliae) (Mattila et al. 1989). On the contrary, fin whales in the North Atlantic are believed to be divided into several subpopulations (Berube et al. 1998). Data on the sex of fin whales obtained from whaling records have been used to estimate the sex ratio in many areas, including the Gulf of Alaska and the Bering Sea, West Greenland, and the northwestern and northeastern North Atlantic (Aguilar and Lockyer 1987, Kapel 1979, Mitchell 1974, Tarasevich 1967). A recent study of the North Atlantic and Mediterranean Sea fin whales detected an even sex ratio for all but two sampling areas (BCrubC et a/. 1998). The first skewed sex ratio was detected in a sample of 33 Icelandic fin whales taken during whaling operations prior to the international moratorium on 372 MARINE MAMMAL SCIENCE, VOL. 17, NO. 2, 2001 commercial whaling. The second was found during the analysis of 109 skin biopsies collected from free-ranging fin whales in the Gulf of St. Lawrence. While the female-biased sex ratio detected in the Icelandic samples might be due to whalers' preference (females are larger than males), the overrepresentation of males in the Gulf of St. Lawrence raises different questions and requires additional scrutiny. In this study we investigate whether the observed male-biased sex ratio in the Gulf of St. Lawrence might be the result of temporal, geographical, or group structure segregation.

Berubé, M., C.L. Berchok and R. Sears. 2001. Observation of a male-biased sex ratio in the Gulf of St. Lawrence fin whales (Balaenoptera physalus): Temporal, geographical, or group structure segregation? Mar. Mamm. Sci. 17(2):371-380.
Observation of a male-biased sex ratio in the Gulf of St. Lawrence fin whales (Balaenoptera physalus): Temporal, geographical, or group structure segregation? PDF (565 KB)