Coryphaenoides cinereus (Gilbert, 1896)

[Japanese name: Karafuto-sokodara]

(Figs. 103–106; Table 7; Appendix 3-6B)

Macrurus cinereus Gilbert, 1896:457 [original description; numerous syntypes; type locality: North Pacific off Unalaska and Ookamok Islands, Albatross sta. 3307, 3329 and 3340, in 399–1033 ftm (730–1889 m)].

Coryphaenoides cinereus: Gilbert & Hubbs 1916:167 (new combination; first record from Japan; brief description; 2 spec. from Okhotsk Sea); Taranetz 1937:169 (listed; Soviet Far East); Okada & Matsubara 1938:449 (in key; Japan; new Japanese name: “Karafuto-sokodara”); Matsubara 1955:1309 (in key; Japan); Lindberg 1959 (listed; southern Okhotsk Sea); Ueno 1965:19 (listed; Hokkaido); Okamura 1970a:129, pl. XXVIII, text-fig. 52 (description; biological notes; 10 spec. from Pacific off Tohoku and Choshi); Ueno 1971:101 (listed; Hokkaido); Tominaga & Uyeno 1981:489 (listed; Japan); Hikita 1981:78, fig. 1 (spec. from Okhotsk Sea off Shiretoko Peninsula); Shiogaki 1982:33 (listed; Aomori Pref.); Sawada 1983:111, 194, 249, figs. 62, 139 (brief description; 8 spec. from Pacific off Tohoku and Okhotsk Sea); Ohta 1983: tables A–B (listed with a question mark; Suruga Bay; in situ observation); Amaoka & Nakaya 1983:45, fig. 61 (compiled; northern Japan); Okamura 1984b:95, pl. 82, fig. D (compiled); Okamura 1988:95, pl. 82, fig. D (compiled); Iwamoto 1990:207, fig. 482 (synopsis); Maeda & Maruyama 1991:366 (listed; Hokkaido); Endo et al. 1993:222, fig. 3 (larval description; 9 spec. from North Pacific); Nakabo 1993:364 (in key); Amaoka et al. 1995:102, fig. 152 (compiled; northern Japan); Miya et al. 1995: table 2 (1 spec. from off Boso Peninsula; midwater capture); Shinohara et al. 1996:169 (2 spec. listed from Pacific off Tohoku); Okamura 1997:126, fig. 1 (compiled); Shinohara & Matsuura 1997:291 (listed; Suruga Bay); Goto 2000:6 (1 spec. from Iwate Pref.); Nakabo 2000:428 (in key; Japan); Nakabo 2002:428 (in key; Japan); Maeda & Tsutsui 2003:488 (listed; Hokkaido); Shiogaki et al. 2004:55 (listed; Pacific off Aomori Pref.); Senou 2008:368, fig. 31.37 (in situ observation; east of Hokkaido); Kitagawa et al. 2008:40, unnumbered fig. (brief description; spec. from Pacific off Tohoku); Shinohara et al. 2009:708 (1 spec. listed from Pacific off Tohoku); Amaoka et al. 2011:130, fig. 164 (compiled; Hokkaido); Nakabo & Kai 2013:504 (in key; Japan); Shinohara et al. 2020:8 (description; 1 spec. from Kurile-Kamchatka Trench); Amaoka et al. 2020:163, fig. 220 (listed; Hokkaido); Motomura 2020:39 (listed; Japan).

Coryphaenoides filamentosus Okamura, 1970a:133, pl. XXIX, textfig. 53 (original description; holotype: BSKU 14208, from “Tohoku District”; 1 paratype collected with holotype; new Japanese name: “Hokuyo-sokodara”); Tominaga & Uyeno 1981:489 (listed; Japan); Okamura 1984b:95, pl. 345, fig. H (compiled); Okamura 1988:95, pl. 345, fig. H (compiled); Nakabo 1993:364 (in key); Nakabo 2000:428 (in key; Japan); Nakabo 2002:428 (in key; Japan); Shinohara et al. 2009:708 (listed; Pacific off Tohoku); Nakabo & Kai 2013:504 (in key; Japan); Motomura 2020:39 (listed; Japan).

Coryphaenoides (Coryphaenoides) cinereus: Okamura 1970b: table 1 (listed; Japan).

Coryphaenoides (Coryphaenoides) filamentosus: Okamura 1970b: table 1 (listed; Japan).

Diagnosis. Pelvic-fin rays usually 9 (rarely 8 or 10–11). Snout short, slightly protruding beyond upper jaw, tipped with prominent enlarged tubercles; lateral angles of snout armed with small scute-like scales (highly deciduous). Snout width 24–30% HL; internasal width 21–27% HL. No modified scales along head ridges. Mouth large, posterior margin of upper jaw extending to below posterior 1/3 of orbit of beyond (but not reaching hind rim or orbit); upper-jaw length 34–40% HL; lateral corner of mouth not restricted by skin folds. Outermost gill slit moderately wide, length 18–26% HL. Barbel short, length 3–9% HL. Teeth small, conical, in narrow bands in both jaws, none especially enlarged. Body scales covered with short, reclined, needle-like spinules in parallel to subparallel rows; tip of last spinule in each row extending slightly beyond posterior scale margin. Transverse scale rows below first dorsal-fin midbase 6.5–10.5. Dorsal surface of snout narrowly naked posterior to leading edges; underside of head broadly naked from snout tip to vertical under posterior nostril. Height of first dorsal fin 79–106% HL; second spinous ray slightly elongate, finely serrated along its leading edge; first dorsal-fin rays II,10–13. Outer pelvic-fin ray greatly prolonged, its tip extending well beyond anal-fin origin. Body pale to dusky.

Material examined. 37 specimens. Syntypes of Macrurus cinereus: CAS-SU 3084 (3, 40.9–69.4 mm HL, 230+–382+ mm TL), south of Chirikof Island, Alaska, North Pacific, 55.4333ºN, 155.4333ºW, 695 ftm (1272 m), Albatross sta. 3340, 29 Aug. 1890 . Holotype of Coryphaenoides filamentosus: BSKU 14208 (67.9 mm HL, 426+ mm TL), off east coast of Japan, no further information. Paratype of C. filamentosus: BSKU 14209 (61.5 mm HL, 350+ mm TL), collected with holotype. Non-types: Japan : BSKU 86816 (1, 81.1 mm HL, 466+ mm TL), southwest of Okino-shima Island, 32.4033ºN, 132.2671ºE, 1501–1516 m, R/ V Tansei-maru, cr. KT-99- 18, sta. BT-4, coll. H. Endo and S. Nagatomo, 16 Dec. 1999 ; BSKU 86850 (1, 90.8 mm HL, 555+ mm TL), Kumano-nada, 33.7332ºN, 136.5788ºE, 2035–2051 m, R/ V Tansei-maru, cr. KT-99-18, sta. BT-7, beam trawl, coll. H. Endo and S. Nagatomo, 20 Dec. 1999 ; BSKU 97789 (1, 89.5 mm HL, 502+ mm TL), off Kuji, 40.3727ºN, 143.3827ºE, 1923–1995 m, R/ V Tansei-maru, cr. KT-93- 15, sta. M5, 3-m beam trawl, coll. Y. Machida, 18 Nov. 1993 ; BSKU 97757 (1, 81.8 mm HL, 471+ mm TL), BSKU 97763 (1, 79.1 mm HL, 480+ mm TL), BSKU 97765 (1, 88.2 mm HL, 502+ mm TL), south of Cape Erimomisaki, 41.0675ºN, 143.3268ºE, 2022–2027 m, R/ V Tansei-maru, cr. KT-08-27, sta. S-2, 3-m ORE beam trawl, coll. H. Endo and N. Nakayama, 20 Oct. 2008 ; BSKU 35706 (1, 73.8 mm HL, 418+ mm TL), BSKU 35708 (1, 81.1 mm HL, 462 mm TL), BSKU 35710 (1, 85.3 mm HL, 472+ mm TL), off Kesennuma, 38.7333ºN, 143.1850ºE, 1950–1960 m, R/ V Hakuho-maru, cr. KH-81-4, sta. 8, 25 Jul. 1981 ; BSKU 96497 (1, 92.5 mm HL, 543+ mm TL), off Kinkazan, 38.4640ºN, 143.0518ºE, 1853–1906 m, R/ V Tansei-maru, cr. KT-08-27, sta. K-2, 3-m ORE beam trawl, coll. H. Endo and N. Nakayama, 23 Oct. 2008 ; * BSKU 96471 (1, ca. 31 mm HL, 140+ mm TL), off Kinkazan, 38.4647ºN, 143.5283ºE, 3137–3223 m, R/ V Tansei-maru, cr. KT-08-27, sta. K-4, 3-m ORE beam trawl, coll. H. Endo and N. Nakayama, 23 Oct. 2008 ; BSKU 97748 (1, 31.9 mm HL, 180+ mm TL), off Kuji, 40.0613ºN, 142.6825ºE, 1005–1016 m, R/ V Tansei-maru, cr. KT-93-15, sta. M3, 3-m beam trawl, coll. Y. Machida, 18 Nov. 1993 ; BSKU 97852 (1, 49.2 mm HL, 291+ mm TL), BSKU 97861 (1, 36.8 mm HL, 164+ mm TL), off Rikuzen-Takata, 39.0538ºN, 142.6342ºE, 1195–1202 m, R/ V Tansei-maru, cr. KT-89-3, sta. SR91, 3-m beam trawl, 10 Mar. 1989 ; BSKU 97833 (1, 36.5 mm HL, 214+ mm TL), off Kamaishi, 39.1444ºN, 142.3748ºE, 847–935 m, R/ V Tansei-maru, cr. KT-89-3, sta. SR89, 3-m beam trawl, 10 Mar. 1989 ; BSKU 58779 (1, 82.7 mm HL, 492+ mm TL), off Kuril Islands, 43.0630ºN, 147.1152ºE, 451– 661 m, FRV Wakataka-maru, sta. G06, coll. D. Kitagawa, 21 Jun. 1996 ; BSKU 97733 (1, 63.6 mm HL, 362+ mm TL), BSKU 97771 (1, 59.5 mm HL, 328+ mm TL), BSKU 97773 (1, 48.2 mm HL, 290+ mm TL), BSKU 97774 (1, 58.1 mm HL, 338+ mm TL), BSKU 97776 (1, 57.8 mm HL, 344 mm TL), BSKU 97788 (1, 51.8 mm HL, 290+ mm TL), south-southeast of Akkeshi, 42.6052ºN, 144.9938ºE, 1113–1161 m, R/ V Tansei-maru, cr. KT-93-15, sta. T8, 3-m ORE beam trawl, coll. Y. Machida, 16 Nov. 1993 ; BSKU 96392 (1, 75.7 mm HL, 440+ mm TL), BSKU 96401 (1, 89.3 mm HL, 487+ mm TL), BSKU 96405 (1, 74.0 mm HL, 406+ mm TL), south of Cape Erimomisaki, 41.6675ºN, 143.3268ºE, 2022–2027 m, R/ V Tansei-maru, cr. KT-08-27, sta. S-2, 3-m ORE beam trawl, coll. H. Endo and N. Nakayama, 20 Oct. 2008 ; BSKU 97780 (1, 65.4 mm HL, 391+ mm TL), BSKU 97792 (1, 60.1 mm HL, 348+ mm TL), Pacific off northern Japan, R/ V Tanseimaru, cr. KT-93-15, 3-m beam trawl, coll. Y. Machida, date unknown ; * BSKU 49888 (1, 56.4 mm HL, 296+ mm TL), Japan, 1500 m, R/ V Hakuho-maru, cr. KH-91-6, sta. 12, 16 Nov. 1991 ; NSMT-P 90682 (4, 64.6–74.1 mm HL, 276+–437+ mm TL), Kitami-Yamato Bank, Okhotsk Sea, coll. H. Matsubara, 2 Jun. 2008.

Counts and measurements. See Table 7.

Size. Attains about 57 cm TL (HUMZ 88325, 565 mm TL, Bering Sea).

Sexual dimorphism. The pelvic-fin length is sexually dimorphic, with males having a longer outer ray than those of similar-sized females (Gilbert & Hubbs 1920; Iwamoto & Stein 1974; Iwamoto 1990).

Development. Larval morphology was described by Endo et al. (1993).

Distribution. Widely distributed in the North Pacific from Japan to the United States, including the Okhotsk and Bering Seas as well as the Emperor Seamounts, at depths of 135–3223 m (Iwamoto & Stein 1974; Borets 1986; Iwamoto 1990; Mecklenburg et al. 2002; Orlov & Tokranov 2008; this study). In Japanese waters, known fromoffthePacificcoastssouthwardtoMiyazaki(31.90ºN) and the southern Okhotsk Sea at depths of 350‾ 3223 m (Appendix 3-6B). Abundant in northern Japan, but rare in the west of the Boso Peninsula (139.89ºE).

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*Abbreviations: 1D.—first dorsal fin; 2D.—second dorsal fin; A.—anal fin; GR—gill rakers; HT—holotype; NT—non-type; P.—pectoral fin; PMX—premaxillary; PT—paratype; ST—syntype; V.—pelvic fin

Remarks. Coryphaenoides cinereus was originally described by Gilbert (1896) based on “numerous specimens” collected from the North Pacific off Unalaska and Ookamok Islands (Fig. 104). This species has been well described by previous authors, and thus there is no need for repetition here. For a full description see Okamura (1970a) and Iwamoto & Stein (1974). This species is one of the most abundant continental slope fishes found in the North Pacific (Orlov & Tokranov 2008), with the highest abundance in the Bering Sea, Kamchatka, and the Okhotsk Sea (Iwamoto & Stein 1974). Orlov & Tokranov (2008) provided detailed information on the biology of this species off the Kuril and Kamchatka Islands.

Geographical variations between the Japanese and Bering Sea populations of C. cinereus have been noted by several authors (Gilbert & Hubbs 1916, 1920; Okamura 1970a; Iwamoto & Stein 1974; Iwamoto 1990), and some were reconfirmed in this study. The Japanese specimens examined have a slightly longer abdomen than three syntypes collected from Alaska, with a longer preanus length (137–164% HL vs. 132–142%), isthmus–pelvic distance (35–45% HL vs. 30–32%), isthmus–anal distance (79–103% HL vs. 69–74%), and pelvic–anal distance (40–62% HL vs. 38–42%). Paired fins of the Japanese specimens examined are also longer than the syntypes, viz., pelvic-fin length (68–113% HL vs. 66–70%) and pectoral-fin length (64–86% HL vs. 60%). These differences are tentatively considered to be geographical variation within a single species, although more Alaskan specimens should be examined to warrant this conclusion.

Nomenclatural discussion. Okamura (1970a) described C. filamentosus based on two specimens collected from off the “east coast of Japan ” (Fig. 105). Unfortunately, no further information is available on the type locality. Okamura (1970a) considered C. filamentosus to be closely similar to C. cinereus, one of the most common grenadiers found in the area. In his key to species of Japanese Coryphaenoides, C. filamentosus is distinguished from C. cinereus by the following combination of features: head bones firm (vs. soft in C. cinereus); body depth greater than postrostral length (vs. about equal to postrostral); spinules on the body scales arranged in divergent rows (vs. parallel rows); interorbital width greater than orbit diameter (vs. less than orbit diameter); upper-jaw length equal to 1/3 HL (vs. distinctly longer than 1/3 HL); orbit diameter 1.8 in postrostral length (vs. 1.4–1.6); barbel length 3.1–3.3 in orbit diameter (vs. 4.5–6.0).

An examination of the types of C. filamentosus, along with 33 specimens of C. cinereus including three syntypes, revealed no significant differences between the two species. They could not be distinguished from each other by meristic and morphometric characters, including those Okamura (1970a) considered as diagnostic characters for separating the two species, viz., body depth, interorbital width, upper-jaw length, orbit diameter, and barbel length (Table 7). The head bones of C. filamentosus are not firm (distinctly soft), but this is probably due to lengthy preservation in formalin. Furthermore, in the additional specimens of C. cinereus examined, the spinules are often arranged in weakly divergent rows (Fig. 106E); the condition is almost consistent with Okamura’s (1970a) illustration for C. filamentosus (text-fig. 53). The close similarity of the two species is amply sufficient to warrant their conspecificity, and C. filamentosus is therefore regarded as a junior synonym of C. cinereus .

Relationships and comparisons. Coryphaenoides cinereus belongs to the subgenus Coryphaenoides (sensu Iwamoto 1990), and is most similar to C. filifer (Gilbert, 1896) widely distributed in the North Pacific. It differs from C. filifer in having a much broader snout (snout width 24–30% HL vs. 19–22%; internasal width 21–27% HL vs. 16–18%), a longer preoral (13–19% vs. 11–13%), and a shorter chin barbel (3–9% HL vs. 8–11%) In C. cinereus, the body scales are covered with short, reclined, needlelike spinules in parallel to subparallel rows (Fig. 106A, C, E), whereas in C. filifer, the spinules are arranged in narrowly divergent rows (Fig. 109). Furthermore, they are distinguished from each other in the presence/absence of open pores along the cephalic sensory canals: the canals are completely closed in C. cinereus, whereas in C. filifer small and inconspicuous pores are present at least along the supraorbital, infraorbital, and preopercular canals.