海洋生物学と海洋学のジャーナル

Omura's whale Balaenoptera omurai stranding on Qeshm Island, Iran, Persian Gulf:Further Evidence for a Wide (Sub) Tropical Distribution

Sharif Ranjbar, Seyed Mohammad H Dakhteh and Koen Van Waerebeek

Omura's whale Balaenoptera omurai stranding on Qeshm Island, Iran, Persian Gulf:Further Evidence for a Wide (Sub) Tropical Distribution

A juvenile rorqual live-stranded on Qeshm Island, Iran, in the northern Strait of Hormuz, Persian Gulf, in September 2007. The cause of stranding remains unknown but the whale (QE22.09.2007) showed no severe traumatic injuries nor was it emaciated. Six key morphological features, diagnostic in combination, allow positive identification as Omura's whale Balaenoptera omurai, a species that has not before been reported from the NW Indian Ocean. Features include diminutive body size (397 cm); an unusually large number of ventral grooves (n=82) and grooves near the midline extended caudad of the umbilicus; a strongly falcate, pointed dorsal fin; asymmetric colouration of the head (especially lower jaws) reminiscent of fin whale, and unilateral dark (eye, ear, flipper-toflank)stripes; faint/incomplete lateral rostral ridges; and extremely low number of short, broad baleen plates (204 in right jaw). The likelihood for the existence of a local B. omurai population in the eastern Persian Gulf or Arabian Sea is deemed higher than the wandering of a small juvenile or mother/calf pair from any of the known distant distribution areas in the eastern or south-western Indian Ocean. This is the first record of Omura's whale for the Persian Gulf and Iran. Combined with two recent strandings of similar juveniles in the Atlantic (Mauritania, Brazil) it suggests that B. omurai may have a significantly wider (sub) tropical distribution than hitherto assumed.