Abstract
A new species of deep-water dogfish shark, Squalus shiraiisp. nov., is described herein as endemic to the tropical waters off Southern Japan. This species has been largely misidentified with S. mitsukurii. However, morphological, meristic and morphometric evidence support it to be a separate and undescribed species. Squalus shiraiisp. nov. differs from this species by having body brown in colour dorsally, caudal fin with ventral and dorsal tips markedly tapered and broadly white, dermal denticles uniscuspidate and lanceolate and larger number of precaudal (91–94) and total vertebrae (120–123) (vs. body dark grey to black; caudal fin with ventral and dorsal tips rounded and not white in colour; denticles tricuspidate and rhomboid; 86–90 precaudal and 116–117 total vertebrae). Squalus shiraiisp. nov. is also clearly separated from other Japanese congeners which are herein revisited to include six species, based on the examination of over 150 specimens caught from Japanese waters that were available in ichthyological collections: S. mitsukurii, S. japonicus, S. acutirostris, S. brevirostris and S. suckleyi. Squalus mitsukurii, S. japonicus and S. brevirostris are re-described in detail and the neotype of S. japonicus is herein designated. Squalus acutirostris is treated as a valid species with occurrences in Japan, China and Taiwan and, thus, a provisional diagnosis is given, as well as an updated diagnosis of S. suckleyi. A key to Squalus species from the North-western Pacific Ocean is given and main morphological differences between S. shiraiisp. nov. and the closest related species are discussed.
Highlights
Dogfish sharks of the genus Squalus Linnaeus, 1758 represent commercially-important taxa within the world fish trade, in which individuals are caught through direct or indirect fisheries and traded for consumption of meat, fins and liver oil as primary products
Our results reveal that Squalus shiraii is morphologically similar to species of the “highfin megalops group” (S. albifrons, S. altipinnis, S. formosus and S. notocaudatus) in having dorsal fins conspicuously tall and upright and dorsal-fin spines robust and elongate
Six species of dogfish sharks occur in Japan according to the present study: S. mitsukurii, S. japonicus, S. brevirostris, S. acutirostris, S. suckleyi and S. shiraii sp. nov (Fig. 8)
Summary
Dogfish sharks of the genus Squalus Linnaeus, 1758 represent commercially-important taxa within the world fish trade, in which individuals are caught through direct or indirect fisheries and traded for consumption of meat, fins and liver oil as primary products. Fisheries management and conservation of dogfish sharks are still outstanding as species-specific catch and landing statistics, population threats and trends are not yet acknowledged. Japan represents one of the world’s leading shark fisheries country whose estimated annual shark landing data for between 1992 and 2000 was 19,600–28,700 t (Sonu 1998; Matsunaga et al 2003).
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