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広島大学水畜産学部紀要 7 巻 1 号
1967-07-31 発行
走島の漁業 : Ⅱ. ウマヅラハギNavodon modestus(GÜNTHER)の産卵生態
Fisheries in Hashiri-shima : II. Spawning of a file-fish, Navodon modestus (GÜNTHER)
村上 豊
遠部 卓
Abstract
瀬戸内海中央部における重要魚類の産卵生態に関する研究の一環として，備後灘におけるウマヅラハギNavodon modestus (GÜNTHER) の産卵について調査を行なった.
備後灘では毎年4-6月の3ヶ月間にわたって，主として島嶼部周辺に設置される桝網によって，多量に本種が漁獲される.この時期のウマヅラハギは，発達した卵巣を有するから，産卵群と考えられる.
3月より5月までにえられた数標本の卵巣を観察すると，時期の推移とともに卵巣の急速な発達がみられる.卵巣卵の卵径頻度分布からみると，本種の産卵はl同で終わるものではないことが推定された.
ウマヅラハギの漁獲量は岸寄りの網に多く沖合の網lこ少ないこと，またその卵の性質などからみて，本種は島嶼部の沿岸で産卵するものと推定し，島艇部周辺のガラモ場よりガラモおよび底質を採集して産着卵の有無を精査した.
1963年6月初旬，走島のガラモ中より92個の卵が発見されたが，これらは形態，構造，大きさなどから，ウマヅラハギ卵と同定された.このことから，ウマヅラハキ、は，少なくとも島嶼部沿岸のガラモ場を産卵場として利用していることが明らかとなった.
なお，ウマヅラハギの卵は，天然では室内で観察されるような強い粘着性を示さない可能性のあることを示唆した.
備後灘では毎年4-6月の3ヶ月間にわたって，主として島嶼部周辺に設置される桝網によって，多量に本種が漁獲される.この時期のウマヅラハギは，発達した卵巣を有するから，産卵群と考えられる.
3月より5月までにえられた数標本の卵巣を観察すると，時期の推移とともに卵巣の急速な発達がみられる.卵巣卵の卵径頻度分布からみると，本種の産卵はl同で終わるものではないことが推定された.
ウマヅラハギの漁獲量は岸寄りの網に多く沖合の網lこ少ないこと，またその卵の性質などからみて，本種は島嶼部の沿岸で産卵するものと推定し，島艇部周辺のガラモ場よりガラモおよび底質を採集して産着卵の有無を精査した.
1963年6月初旬，走島のガラモ中より92個の卵が発見されたが，これらは形態，構造，大きさなどから，ウマヅラハギ卵と同定された.このことから，ウマヅラハキ、は，少なくとも島嶼部沿岸のガラモ場を産卵場として利用していることが明らかとなった.
なお，ウマヅラハギの卵は，天然では室内で観察されるような強い粘着性を示さない可能性のあることを示唆した.
Abstract
A study was carried out to clarify the spawning of a file-fish, Navodon modestus (GÜNTHER), in the Bingo Nada area, as a serial study on the spawning ecology of the commercially important fishes in the central part of the Inland Sea of Japan.
As described in previous paper, the file-fish are caught abundantly by the masu-ami, a kind of pound net, in Bingo Nada, operated during the three months from April until June. Since most of the fish in these months have well developed gonads, they are considered to be spawners.
Observations on ovaries of several samples taken at different times from March through May indicated a rapid development of ovaries during the period. From the analysis of the frequency distribution of diameter of ovarian eggs, the spawning of Navodon modestus may occur at least more than once during the spawning season.
On the basis of the catch records and from the nature of the eggs of the aluterid fishes in general, it was presumed that the file-fish may spawn somewhere along the coasts of islands in Bingo Nada. Efforts had been devoted to find the eggs spawned in nature, especially in Sargassum zones along several islands. A large amount of Sargassum, together with the bottom sediments nearby, were collected at low water and thoroughly examined. Finally, in early June, 1963, 92 eggs were found among Sargassum serratifolium collected near St. I, located at south-western coast of Hashiri-shima.
These eggs were identical in structure and size with the eggs of Navodon modestus obtained by artificial fertilization. It was thus made clear that some of the file-fish may spawn in Sargassum zones.
A consideration was given on the possibility that the eggs of Navodon modestus may not so firmly adhere to substrates in nature as in the laboratory.
As described in previous paper, the file-fish are caught abundantly by the masu-ami, a kind of pound net, in Bingo Nada, operated during the three months from April until June. Since most of the fish in these months have well developed gonads, they are considered to be spawners.
Observations on ovaries of several samples taken at different times from March through May indicated a rapid development of ovaries during the period. From the analysis of the frequency distribution of diameter of ovarian eggs, the spawning of Navodon modestus may occur at least more than once during the spawning season.
On the basis of the catch records and from the nature of the eggs of the aluterid fishes in general, it was presumed that the file-fish may spawn somewhere along the coasts of islands in Bingo Nada. Efforts had been devoted to find the eggs spawned in nature, especially in Sargassum zones along several islands. A large amount of Sargassum, together with the bottom sediments nearby, were collected at low water and thoroughly examined. Finally, in early June, 1963, 92 eggs were found among Sargassum serratifolium collected near St. I, located at south-western coast of Hashiri-shima.
These eggs were identical in structure and size with the eggs of Navodon modestus obtained by artificial fertilization. It was thus made clear that some of the file-fish may spawn in Sargassum zones.
A consideration was given on the possibility that the eggs of Navodon modestus may not so firmly adhere to substrates in nature as in the laboratory.
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