Further description and notes of natural history of the viper dogfish, Trigonognathus kabeyai from the Kumano-nada Sea and the Ogasawara Islands, Japan (Chondrichthyes: Etmopteridae)

The viper dogfish, Trigonognathus kabeyai is further described on the basis of 19 male [176–470 mm in total length (TL)] and 13 female (325–539 mm TL) specimens collected from the Kumano-nada Sea. In addition, the holotype, paratype, and seven specimens collected from the stomachs of Taractichthys steindachneri and Thunnus obseus from the Ogasawara Islands, Japan, were also examined. This is the first description of large (adult) specimens. The allometric size-on-size equation Y = aX b was used to determine morphometric growth patterns, positive allometry, negative allometry, and isometry. Size at maturity was about 430 mm TL for males and about 520 mm TL for females. Myctophid fishes consisting of Diaphus gigas, Diaphus spp., Benthosema fibulatum, and Benthosema sp. were the only identifiable prey in the stomachs of Trigonognathus kabeyai examined. Most of the prey fishes were found almost intact and usually had puncture holes made by teeth. On the basis of stomach content and jaw morphology, this species is thought to be a ram feeder.