The vertex of the skull is regarded as one of the most important categorical traits in taxonomy in baleen whales. However the previously reported species-specific characteristics for the North Pacific common minke whale, were based on only a very limited number of specimens Therefore, we aimed to assess the efficacy of these morphological characteristics as categorical traits, based on specimens of North Pacific common minke whales collected from the JARPNII survey（n =106）. The frontal border of the nasal bones, as well as the positional relationship of the end of premaxilla and the nasal bones, were varied widely by individual, indicating that these traits are not appropriate for species classification. However, the end of the maxilla was located posteriorly to the end of the premaxilla and the nasal bones in all whales surveyed. Therefore, we conclude that this characteristics can serve as universal species-specific morphological characteristics for the North Pacific common minke whales. Furthermore, we found an interparietal bone in all whales surveyed. This bone has been regarded as one of the specific character of “dwarf” minke and have not been reported from any common minke whales in the North Pacific.
The Furuhama Park, which was improved and developed artificially in 2004 at Heiwajima artificial island of Ota City, is located at the innermost part of Tokyo Bay. The Park is composed of the tidal flat（1ha）and sandy beach（1.2ha）in east and west, respectively, with a shallow water area（4.6ha）between them, and separated from the outside canal by submerged dikes. Monthly samplings of fishes were carried out in both the tidal flat and sandy beach by using the small seine-net from May 2014 to June 2015. A total of 31,736 individuals representing 35
species of 18 families were collected, almost all of them being larvae or juveniles. No remarkable differences were detected between the tidal flat and sandy beach from the viewpoint of numbers of species and individuals per towing and species compositions. Three gobiids, Acanthogobius flavimanus, A. lactipes and Gymnogobius breunigii, were determined as resident species. The numbers of marine fishes and ayu Plecoglossus altivelis altivelis, usually drifted by tidal/shore currents and being dominant at shorelines of the inner Tokyo Bay in summer and winter, respectively, were relatively low when comparing with other areas. This study suggested that the Furuhama Park would provide diverse habitats for estuarine fishes, but the insufficient water circulation would make the Park unsuitable habitats for marine fishes.