BREEDING AREAS AND SOUTHBOUND MIGRATIONS OF SOUTHERN MINKE WHALES BALAENOPTERA-ACUTOROSTRATA

Southern minke whales Balaenoptera acutorostrata are genetically separ ated from Northern Hemisphere minke whales. Seasonal migrations take t hem from tropical latitudes in winter to high latitudes of the Antarct ic in summer. Breeding takes place in warmer waters but little is know n of breeding areas. Breeding areas and southbound migrations were stu died using sighting data derived from the Japanese sighting surveys du ring 1976 to 1987. Relatively higher concentrations were observed in t he waters mainly around 10 degrees to 20 degrees S in October, the end of the main conception period of this species in the Southern Hemisph ere. Spatial distribution in tropical and subtropical waters during th e latter half of the conception period suggests that there are 2 breed ing areas in the eastern and western South Pacific and 2 others in the eastern and western Indian Ocean. It appears that breeding population s of the southern minke whale are relatively dispersed in open waters while coastal species such as right whales Eubalaena glacialis, humpba ck whales Megaptera novaeangliae and gray whales Eschrichtius robustus migrate along the shore and congregate in near-shore breeding areas. Latitudinal occurrences by month suggest that southern minke whales mo ved southward from the breeding areas by October-November, and that mo st of them had migrated into Antarctic waters by January. They tend to move almost directly south from the breeding areas to feeding areas, and subsequently disperse after arriving at the feeding areas. Southbo und migration speeds were estimated to average 20 nautical mites (n mi les) d(-1) in waters north of the subtropical convergence and 40 to 50 n miles d(-1) in waters south of the convergence.