During the process of the recent description of a new balaenopterid species, the Omura’s whale, Balaenoptera omurai Wada, Oishi et Yamada, 2003, the authors proposed to separate the so-called “Bryde’s whale”, Balaenoptera edeni Anderson, 1878/9 into the Eden’s whale, B. edeni and Bryde’s whale (s.s.), Balaenoptera brydei Olsen, 1913. In their project of the investigation on the middle sized balaenopterid whales in Taiwan and Thailand, the authors confirmed many specimens classified into the three species. In addition to the characteristics on the vertex of the skull, the morphology of the lateral surface of the braincase around the alisphenoid has been clarified to be available for distinction among the three species according as the specimens for comparison increase. The balaenopterid specimens, formerly reported as the so-called “Bryde’s whale”, B. edeni which are preserved in the Wakayama Prefectural Museum of Natural History (Wakayama specimen) and Kitsuki City Library in Oita Prefecture (Kitsuki specimen), are judged to be assignable to the Eden’s whale, B. edeni based on the comparison of the vertex and alisphenoid morphology of the formerly described specimens including the holotype of B. edeni.
Following a previous paper (Honma and Kogawara,2008), sighting records of whales by Sado Line (Sado Kisen) jetfoils and car ferry boats operating on the Niigata－Ryotsu route, Sado Strait, Sea of Japan, were compiled from February to December, 2007. Compariosn was made among the instances of previous years investigated 1994－2006. Sixty-nine instances, comprising 21 car ferry and 48 jetfoil obserfvations, were enumerated. These numbers were the largest than those of the previous years. Two to four sighting records of different individuals in a day were secured fourteen occasions throughout the investigation period. The greatest numbers of sightings was May, like those of ordinary year, except March in 2006. The time zone of higher frequencies was concentrated in 10 a.m. and in 2 p.m. The directionns in which the whales were swimming (= migrating route) were noted in 32 instances, consisting of 11 north,18 south, and 3 others. There was no occurrence of collision with cetaceans and other unknown large subjects in 2007.
In spring, the Pacific white-sided dolphin (PWS) comes to the Tsugaru Strait and is observed mostly from April to June. In this study, we analyzed the data of sighting surveys conducted from ferry vessels between Hakodate and Aomori from May 2003 to August 2008, and examined the migration of PWS in the strait. The distribution of PWS differed among periods. In March, April and early May, PWS was observed in the northern part of the Tsugaru Strait. Between mid-May and mid-June, distribution of PWS expanded to all of Tsugaru Strait. Between late June and July, PWS was observed in southern part of the Tsugaru Strait. Subsequently, PWS was not observed. Such migration pattern was found in all survey years.
During mid-April to early May in 2005, a gray whale occurred in Tokyo bay. On May 11, the animal was finally caught at a set net 1km off Tomiyama, Minami Boso city at the entrance of Tokyo bay. We observed the animal at three occasions in the areas off Sodegaura, Narashino, and between Yokosuka and Yokohama. In those waters, the animal occurred at inshore shallow waters, off 50 m to 100 m in Sodegaura, off 10 m to 100 m in Narashino, off 100 m to 1,400 m (depth between 11 m and 18 m) between Yokosuka and Yokohama. The anima1 presumably tried to feed both in Sodegaura and Narashino areas, and simply cruised between Yokosuka and Yokohama. It was suspected that the animal strayed into Tokyo bay on the way up to the feeding ground in the north. Psossibilities of the preference of feeding on the muddy bottom and instinctive traveling to the north were suspected.