Japan. J. Ichthyol. 魚 類 学 雑 誌 41(2): 222-226, 1 9 94 41 (2): 222-226, 1 9 94

Occurrence of Juveniles of Two Bathymasterid from Hokkaido, Japan

Hisayoshi Wakimoto and Kunio Amaoka

Laboratory of Marine Zoology,Faculty of , HokkaidoUniversity, 3-1-1 Minato-cho,Hakodate, Hokkaido 041, Japan

(ReceivedNovember 26, 1993; in revisedform March 24, 1994; acceptedJune 13, 1994)

The bathymasterid is a com- pact group represented by four species (B. signatus Cope 1873; B. leurolepis McPhail 1965; B. derjugini Fig. 1. Collection localities (•œ) of bathymasterid Lindberg 1930; and B. caeruleofasciatus Gilbert and juveniles. Burke 1912) distributed around the littoral zone of the northern North Pacific, with the first three spe-

cies being known from Japanese waters (Sato, 1940; (A), pectoral fin rays (P1), myomeres (MN), gill McPhail, 1965; Shinohara et al., 1992). Information rakers (GR), and vertebrae (V). on larvae and juveniles of these is limited. Kashkina (1970) and Grigor'ev (1992) reported ju- Bathymaster derjugini Lindberg, 1930 venile specimens as Bathymaster sp. from the Bering sea and Sea of Okhotsk, Matarese et al. (1989) (Fig. 2A) described the identification of juvenile bathymaster- Material. Three specimens (juvenile stage). HUMZ-L ids, and Shiogaki (1993) described post-flexion larva 5397, 32.7mm SL, 41•‹60.0'N, 144•‹00.2'E (off Hiroo, Hok- kaido, Japan), Apr. 4, 1992, larva net; HUMZ-L 5398, 37.0 of B. derjugini taken from Japan. mm SL, collected with HUMZ-L 5397; HUMZ-L 5399, During the cruise to eastern Hokkaido of the T/S 30.9mm SL, 42•‹30.1'N, 144•‹15.0'E (off Hiroo, Hokkaido, Hokusei-Maru of Hokkaido University in April Japan), Apr. 5, 1992, larva net. 1992, four juvenile specimens of B. derjugini and B. Diagnosis. Long caudal peduncle. Large pecto- leurolepis were obtained by larva net. Subsequently, ral fin extending just beyond anus. Melanophores two juvenile specimens of B. leurolepis were found in around urostyle. Caudal vertebrae 34. Minute ex- a collection of larvae obtained off the coast of Usu- ternal melanophores on operculum. jiri, southwestern Hokkaido, Japan by luring light in April 1984 (Fig. 1). This paper documents Description. Proportional measurements and and describe these juveniles in detail. counts are shown in Table 1. Body elongated, later- ally compressed. Anus anterior to midpoint of body,

Materials and Methods just before anal fin origin. Caudal peduncle long. Posterior margin of upper jaw extending to a vertical The specimens are preserved in 5% formalin and through anterior margin of pupil. Many sensory

maintained in the larval collection of the Laboratory pores on head; infraorbital pores 12, supraorbital

of Marine Zoology, Faculty of Fisheries, Hokkaido pores 5, interorbital pore 1, preopercular pores 6, University (HUMZ-L). Observations were made mandibular pores 3. All fins formed; pectoral fin under binocular microscope. The standard length of large, posterior margin extending beyond anus; specimens was measured by calipers, and detailed pelvic fin jugular. Branchiostegal membrane sepa- measurements of body parts by Toolmaker's micro- rated from isthmus, with 6 rays. Gill rakers on outer scope. The following abbreviations are used; stan- side of first arch 5+14, moderately long; those on dard length (SL), head length (HL), body depth inner side 3+10, short with small spines on their (BD), preanus length (PAL), snout length (SnL), tips. eye diameter (ED), dorsal fin rays (D), anal fin rays Large melanophores thickly covering occiput, ab-

•\2 2 2•\ Bathymasterid Juveniles

A

B

Fig. 2. Lateral views of bathymasterid juveniles. A) Bathymaster derjugini, HUMZ-L 5398, 37.0mm SL; B) B. leurolepis, HUMZ-L 5396, 36.3mm SL. Scale indicates 10mm.

domen. Single row of large melanophores on each (1990), adult B. derjugini differ from other members side of dorsal midline. No pigment row on ventral of the genus in having a black blotch on the opercu- side of abdomen. Melanophores scattered along base lum, and lower counts of dorsal fin rays (fewer than of anal fin, becoming dense on caudal peduncle. 45) and caudal vertebrae (fewer than 35) (Table 2). Small melanophores along lateral midline of caudal The present specimens were identified as B. derjugini peduncle, base of caudal fin and urostyle (Fig. 3). owing to their agreement with the above meristic Internal melanophores on vertebrae of posterior characters, in addition to having some minute exter- caudal region. A few large, internal melanophores nal melanophores on the operculum (Fig. 4). In and one or two minute, external melanophores on fact, the presence of such melanophores is probably a operculum (Fig. 4). good character by which to identify juveniles of this species. Remarks. The specimens are considered to On the basis of the above characters, a specimen of belong to the genus Bathymaster on the basis of the Bathymaster sp. reported by Grigor'ev (1992) may following characters; long caudal peduncle, large be identified as B. derjugini (Table 2). However, two pectoral fin extending beyond anus, and melano- juveniles reported by Kashkina (1970) could not phores around urostyle (Matarese et al., 1989; Shio- identified to species owing to their meristic counts gaki, 1993). overlapping with those of other bathymasterid According to Sato and Ueno (1953) and Matarese species (Table 2).

Table 1. Proportional measurements and meristic counts of Bathymaster derjugini and B. leurolepis

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A A

B B

Fig. 3. Melanophores around urostyle. A) Bathy- master derjugini; B) B. leurolepis.

Shiogaki (1993) described a row of melanophores along the ventral midline of the abdomen, but such was not observed in the larger specimens examined Fig. 4. Comparison of melanophores on operculum. here, possibly having been lost with growth. A) Bathymaster derjugini; B) B. leurolepis.

luring light; HUMZ-L 3076, 37.5mm SL, collected with Bathymaster leurolepis McPhail, 1965 HUMZ-L 3075; HUMZ-L 5396, 36.3mm SL, 42•‹00.1'N, (Fig. 2B) 143•‹50.1'E (off Hiroo, Hokkaido, Japan), Apr. 4, 1992, larva net. Material. Three specimens(juvenile stage). HUMZ-L 3075, 41.2mm SL, Usujiri, Hokkaido, Apr. 26, 1984,fish Diagnosis. Long caudal peduncle. Large pecto-

Table 2. Comparison of some meristic characters of bathymasterid adults and juveniles

A, adult; J, juvenile.

•\2 2 4•\ Bathymasterid Juveniles

ral fin extending beyond anus. Melanophores around zoogeographic ranges of the two species; the former urostyle. Combination of 18 pectoral fin rays and being widely distributed from northern Japan to the 45-46 dorsal fin rays. Upper jaw extending to middle Gulf of Alaska, with B. caeruleofasciatus being re- of eye. stricted to the northeastern Pacific (McPhail, 1965). Description. Proportional measurements and counts are shown in Table 1. Body elongated, later- Acknowledgments ally compressed. Anus anterior to midpoint of body. We are grateful to Dr. Ann C. Matarese of the Caudal peduncle long. Posterior margin of upper Alaska Fisheries Science Center, National Marine jaw extending to a vertical through middle of eye. Fisheries Service, Seattle, for her critical reading of Many sensory pores on head; infraorbital pores 13, the manuscript and useful comments. We thank the supraorbital pores 5, interorbital pore 1, preoper- Captain Gen Anma and the crew of the T/S Hokusei- cular pores 6, mandibular pores 4. All fins formed; Maru, Hokkaido University for their help in collect- pectoral fin large, posterior margin extending beyond ing materials. We also express our thanks to Dr. anus; pelvic fin jugular. Branchiostegal membrane Mamoru Yabe, Dr. Gento Shinohara, Dr. Tomoyuki separated from isthmus, having 6 rays. Gill rakers 5 Komai and Mr. Hiromitsu Endo (HUMZ) for their +12 on outer and 0+9 on inner sides of first arch. assistance. Large melanophores thickly covering occiput, ab- domen. Single row of large melanophores on each side of dorsal midline. No pigment row on ventral Literature Cited side of abdomen. Melanophores scattered on in- Grigor'ev, S.S. 1992. Larvae of a ronquil,Bathymaster sp. fraorbital region and base of anal fin, becoming (Bathymasteridae)from the Sea of Okhotsk. J. Ichthy- dense on caudal peduncle. Small melanophores ol., 32: 125-128. along lateral midline of caudal peduncle, base of Kashkina, A.A. 1970. Summer ichthyoplanktonof the caudal fin and urostyle (Fig. 3). One internal melano- Bering Sea. Tr. Vsesoyuz.NII morsk. ryb. khoz-va. i okeanografii,70: 225-245. (In Russian.) phore on preoperculum and two on operculum (Fig. Matarese, A.C. 1990. Systematicsand zoogeographyof 4). the ronquils familyBathymasteridae (Teleostei: Percifo- Remarks. In the artificial key suggested by Sato rmes). Unpubl. Ph. D. diss., Univ. of Washington, and Ueno (1953), adult Bathymaster leurolepis was Seattle. 190pp. distinguished from those of B. derjugini and B. signa- Matarese, A.C., A.W. Kendall, Jr., D.M. Blood and B. tus on the basis of the following combination of M. Vinter. 1989. Laboratory guide to early life history characters: 18-19 pectoral fin rays and 44-49 dorsal stages of northeast Pacific fishes. NOAA Tech. Rep. NMFS Cir., (80): 1-652. fin rays. McPhail (1965) separated B. leurolepis McPhail, J.D. 1965. A new ronquil,Bathymaster leurole- from B. caeruleofasciatus owing to the former having pis, from the Aleutian Islands. J. Fish. Res. Bd. Canada, a shorter upper jaw and lacking scales on the pelvic 22: 1293-1297. fin. However, pelvic fin scales are undeveloped and Sato, S. 1940. Note on the fishesof familyBathymasteridae differences in upper jaw length not apparent in larvae in northern Japan. HokkaidoImp. Univ., J. Fac. Sci. VI, and early juveniles of these two species (Matarese, Zool., 7: 95-98. pers. comm.). The distinguishing of juveniles of B. Sato, S. and T. Ueno. 1953. On a rare fish, Bathymaster leurolepis from those of B. caeruleofasciatus is there- signatusCope, taken from the northern Pacific,and notes fore difficult, with further investigation of diagnostic on allied species. Bull. Fac. Fish., Hokkaido Univ., 4: characters of juveniles of the two species being war- 203-211. Shinohara, G., H. Yoshida and M. Yabe. 1992. First ranted. In the present paper, we followed Sato and record of Bathymastersignatus (: Bathyma- Ueno (1953) and McPhail (1965), identifying the steridae) from Japan. Japan. J. Ichthyol., 39: 169-172. present juveniles as B. leurolepis (having 18 pectoral Shiogaki,M. 1993. The studies on the spawningbehavior, fin rays, 45-46 dorsal fin rays and a shorter upper larval morphologyand phylogenyof the northern blenn- jaw). Furthermore, the appearance of juveniles of B. ioidfishes. Unpubl.Ph. D. diss., Univ. of Tokyo,Tokyo. leurolepis from Hokkaido is supported by the known 193pp., 62pls.

•\ 2 2 5•\ H. Wakimoto & K. Amaoka

北 海 道 か ら 得 ら れ た メ ダ マ ウ オ 科2種 の 稚 魚 オ の稚 魚 の鰓 蓋 上 に 黒 色 素 胞 が観 察 さ れ た.こ れ は 成 魚 の 鰓 蓋 上 に存 在 す る 黒斑 が 発 現 し た も の と考 え られ,稚 魚 期 に お け る ス ミツ キ メ ダ マ ウオ の 分 類 形 質 と して の 有 効 性 が 示 唆 され た. 脇 本 久 義 ・尼 岡 邦 夫 ま た,Grigor'ev(1992)に よ って 報 告 され た 未 同定 の メ ダ マ ウ オ 属 稚 魚 は,そ の計 数 形 質 に よ り ス ミツ キ メ ダ マ ウオ で あ る と考 北 海 道 沿 岸 か ら採 集 さ れ た ス ミツ キ メ ダ マ ウオBathymaster え られ た が,Kashkina(1970)が 報 告 した 未 同定 の稚 魚 は そ の計 derjuginと マ ダ ラ メ ダ マ ウオB.leurolepisの 稚 魚 を 記 載 した.ス 数 形 質 が 全 て の 種 と重 複 す る た め,査 定 は不 可能 で あ った. ミツ キ メダ マ ウオ は他 の種 と比 較 して よ り少 な い 尾 椎 骨 数(34) に よ って 査定 され,ま た マ ダ ラ メ ダ マ ウ オ は胸 鰭 鰭 条 数 が18, 背 鰭 鰭 条 数 が45-46,そ して短 い 上 顎 を もつ と い う形 質 の 組 み 合 (〒041函 館 市 港 町3-1-1北 海 道 大 学 水 産 学 部 水 産 動 わ せ に よ り査 定 さ れ た.ま た本 研 究 にお いて,ス ミツキ メ ダマ ウ 物 学 講 座)

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