Golden Sweeper

A marine fish belonging to the order Perciformes and family Caprifoliidae of the class Osteichthyes. It is found in the western Pacific and Indian Oceans, including Hachijo Island, the Pacific coast of Chiba Prefecture to Iojima and Takeshima in Kagoshima Prefecture, the north and northwest coasts of Kyushu, the Nansei Islands south of Okinawa Island, the Ogasawara Islands, Jeju Island (Korea), Taiwan, the Marshall Islands, and the northwest coast of Australia. Its body is long and slender, with its height being approximately 27-31% of its body length. Its eyes are large, with an eye diameter of 13-14% of its body length. Its mouth is large and oblique. The rear end of its upper jaw reaches below the center of the eye. It has 6 gill rakers on the upper branch and 17 on the lower branch. Its lateral scales are strong pectin scales that are difficult to remove. The lateral line extends from the upper end of the gill slit to the base of the tail fin, but does not reach the rear end of the tail fin. The lateral line slits are 63-79. The base of the anal fin is not covered with scales. The dorsal fin is small, located almost in the center of the body, and has 5 spines and 8-10 soft rays. The anal fin begins below the rear end of the dorsal fin base, and has 3 spines and 20-21 soft rays. The length of the anal fin base is short, about 30% of the body length. The rear end of the tail fin is forked. The body is pink and translucent, the ventral surface is silvery white, and the spine is visible through the skin. The rays of each fin are pink, and the fin membrane is transparent. The tips of the upper and lower lobes of the tail fin are black. It lives in coastal rocky and coral reef areas. During the day, they gather in groups under rocks or corals or in holes, but come out at night to feed vigorously. They may be mixed with fishes of the family Acanthidae. They have a light-emitting organ on their ventral surface, which contains a luminous substance and emits light. A small fish measuring 6 cm in length, they are sometimes caught in large quantities using fixed nets, but being small, they have little utility. There are 12 species of the genus Acanthidae known worldwide, but this is the only one found in Japan. This genus can be easily distinguished from the other genus of Acanthidae, Acanthidae, by the fact that the lateral line does not reach the rear end of the caudal fin, there are few soft rays in the anal fin, and there are no scales at the base of the anal fin.

[Masao Katayama and Kunio Amano, February 17, 2021]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

硬骨魚綱スズキ目ハタンポ科に属する海水魚。八丈島、千葉県から鹿児島県硫黄島(いおうとう)・竹島の太平洋沿岸、九州北岸と北西岸、沖縄本島以南の南西諸島、小笠原(おがさわら)諸島、済州島(さいしゅうとう)（韓国）、台湾、マーシャル諸島、オーストラリア北西岸などの西太平洋とインド洋に分布する。体は細長く側扁(そくへん)し、体高は体長のおよそ27～31％。目が大きく、眼径は体長の13～14％。口は大きくて、斜位。上顎(じょうがく)の後端は目の中央部下に達する。鰓耙(さいは)は上枝に6本、下枝に17本。体側鱗(りん)は強い櫛鱗(しつりん)ではがれにくい。側線は鰓孔(さいこう)の上端から尾びれ基底で終わり、尾びれの後端まで達しない。側線孔は63～79。臀(しり)びれの基部は鱗(うろこ)をかぶらない。背びれは小さくて、体のほとんど中央部に位置し、5棘(きょく)8～10軟条。臀びれは背びれ基底の後端下方から始まり、3棘20～21軟条。臀びれ基底長は短く、体長の30％前後。尾びれの後端は二叉(にさ)する。体色は桃色で半透明、腹面は銀白色で、背骨が透けて見える。各ひれの鰭条(きじょう)は桃色で、鰭膜は透明。尾びれの上・下葉の先端は黒い。沿岸の岩礁域やサンゴ礁域にすむ。日中は岩やサンゴの下や穴の中で群れているが、夜間に外に出て、盛んに摂餌(せつじ)する。テンジクダイ科魚類と混成することがある。腹面に発光器をもち、この中に発光物質があり、発光する。体長6センチメートルの小魚で、定置網などで多量に漁獲されることがあるが、小形魚で利用価値は少ない。キンメモドキ属は世界から12種が知られているが、日本からは本種だけである。ハタンポ科のもう1属のハタンポ属魚類とは、本属は側線が尾びれ後端まで達しないこと、臀びれ軟条数が少ないこと、臀びれの基底部に鱗がないことなどで容易に区別できる。

［片山正夫・尼岡邦夫　2021年2月17日］

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