Hymenogadus gracilis Gilbert and Hubbs, 1920

Iwamoto, Tomio, Nakayama, Naohide, Shao, Kwang-Tsao & Table, Hsuan-Ching Ho, 2015, Synopsis of the Grenadier Fishes (Gadiformes; Teleostei) of Taiwan, Proceedings of the California Academy of Sciences 62 (3), pp. 31-126 : 78

Hymenogadus gracilis Gilbert and Hubbs, 1920

Hymenocephalus (Hymenogadus) gracilis Gilbert and Hubbs, 1920:522–525 , fig. 31 (holotype, USNM 78227, 96 TL, off s. Luzon, Philippines, 13 28ʹ45ʺN, 121 01ʹ12ʺE, 162 fm [296 m]).— Marshall and Iwamoto in Marshall, 1973:602–604, fig. 31 (19 spec., nw. Pacific, e. and w. Atlantic; 342–618 m).— Iwamoto and Merrett, 1997:518, fig. 20b.— Shao et al., 2008: table 2 (3 spec., Taiwan [ NET, SCS], 100–950 m)

Hymenogadus gracilis : Okamura, 1970:61–63, pl. XVIII, text-fig. 27 (60 spec., 91–128 mm TL; s. Japan, 300–500 m).— Okamura in Masuda et al., 1984:94, pl. 80H (compiled).— Okamura in Okamura and Kitajima, 1984:201, 359, fig. 143 (p. 200) (3 spec., Okinawa Trough [East China Sea], 295–385 m).— Chiou et al., 2004b:44–45, fig. 13 (2 spec., ne. Taiwan).

MATERIAL EXAMINED (6 spec.).— NET: ASIZP 61229 (1, 118 TL), Nan-fang-ao ; ASIZP 61230 (1, 120 TL), Da-xi ; ASIZP 65565 (1, 60 TL), Da-xi ; ASIZP 70278 (1, 105 TL), Da-xi. Other specimens: ASIZP 68334 (2, 96–112 TL), Aurora, 357– 367 m.

DISTINGUISHING FEATURES.— 1D II9–11; P i14–i17; V 7–9, usually 8; inner GR-I 14–18 total. Body depth 50–60% HL, about 9–10 in TL; barbel long, 20–30% HL. Attains about 130 mm TL.

DISTRIBUTION.— Probably circumglobal in warm seas, but not central e. Pacific, central e. Atlantic, and central Pacific (but see Remarks), in 300– 450 m.

REMARKS.— The taxonomic status of the Hawaiian species H. tenuis Gilbert and Hubbs, 1917 has yet to be resolved. It may be a synonym of H. gracilis . Okamura (1970:58) recognized Hymenogadus as a full genus with two included species, H. gracilis and H. kuronumai , and by implication, also H. tenuis . Okamura also placed H. kuronumai into its own subgenus Spicomacrurus Okamura, 1970 , a taxon that Iwamoto et al. (2011) elevated to full generic status. Hymenogadus gracilis appears to be more characteristic of oceanic elevations, such as islands, seamounts, and ridges, than to continental landmasses, and the terete body form is suggestive of a more pelagic, active-swimming lifestyle (not benthic, as proposed by Okamura 1970:60). Surprisingly, the species was not recorded by Okamura (in Okamura et al. 1982) from the Kyushu-Palau Ridge. Pelagic captures have been reported (Sazonov and Iwamoto 1992) in the upper 300 m over bottom depths of> 1,000 m.