Cetacean fauna and occurrence pattern in the southern Kumano-nada, Pacific coast of western Japan during fall and winter from sighting records obtained by dolphin drive fishery

Abstract

　Kumano-nada is known for its industry in which cetaceans are used as a resource, including whale watching and dolphin fishery. However, information on the cetacean fauna of Kumano-nada remains insufficient. Therefore, in this study, we investigated the cetacean fauna and their occurrence patterns during fall and winter in southern Kumano-nada by analyzing sighting data recorded during dolphin drive fisheries in Taiji, Wakayama, Japan. In total, 22 species (Mysticeti: five species, Odontoceti: 17 species) were identified from 31 fishing season datasets. Thirteen species with relative frequencies of >50% were categorized into four groups: species with a peak occurrence in September–October, species with a peak occurrence in November–December, species with a peak occurrence in January–February, and species without a peak occurrence. Four species for which sighting rates declined owing to the Kuroshio meander were noted, and the distribution of two of these species, short-finned pilot whales and pantropical spotted dolphins, may be strongly affected by the Kuroshio current. In addition, a substantial mixed-species group of melon-headed whales or pygmy killer whales and Fraser’s dolphins was confirmed.