著者

森 浩一郎 船越 進 Mori Koichiro Funakoshi Susumu

出版者

三重大学水産学部

雑誌

三重大学水産学部研究報告 (ISSN:02875772)

巻号頁・発行日

no.8, pp.p97-106, 1981-10

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The present authors have made taxonomical and ecological investigations of the white fish, Salangichthy microdon BLEEKER, in spawning period. The material for this study was collected at Akasuka, Kuwana City, located in the mouth of the Nagara River, during the period of February to April in 1980. The results obtained are summarized as follows. The present specimens were identified as Salangichthys microdon BLEEKER, because of having such specific characteristics as 12~13 dorsal fin rays, 25~27 anal fin rays,14~17 pectoral fin rays, 17~18 anal scales in male, 11~16 mandibular teeth and 7~11 palatine teeth. From the results of the examination of body length, it can be said that males usually exceed females in body length. The range of body length is 60.1~85.3 ㎜ in males and 61.5~79.5 ㎜ in females, and the mean value of the same is 78.6 ㎜ in males and 73.7㎜ in females. The mode of body length in males is 74~76 ㎜ and that in females 68~70㎜. The rerationships between body length (L in ㎜) and body weight (W in g) in males and females are expressed by the following equations : log W = 3.00 log L-5.31 ( r = 0.90) for male, log W = 3.03 log L-5.44( r = 0.87) for females. The condition factors (W/L3 × 106) in seasonal change ranges 4.67~ 5.22 in males and 3.57~4.48 in females, and the values appear somewhat higher in males.The mean value of the gonad indexes (GI=GW/L3×107); GW , gonad weight in g) is 0.124~0.252 in males and 6.21~15.17 in females, and any characteristic tendency was not recognized in the seasonal changes of gonad indexes. The mean value of the egg diameter measured by the season ranges 0.75~0.93 ㎜ with the excepiton of the case in February 19 , the value showed a tendency to somewhat decrease toward the end of the fishing period. Although the number of the ovarian eggs is 153 ~2,040 and largely varies among individuals, no significant correlation between the number of eggs and body length was recognized. Regarding the food of the white fishes, Calanus cinicus is predominantly found in their digestive tract. That Calanus cinicus, one of the marine copepods, is abundantly distributed in the saline bottom waters in the mouth of the Nagara River from November to February.著者等はシラウオについて分類学的検討、および生態学的研究を行い概略次のような結果を得た。なお本研究材料は1980年2月~4月の期間、長良川河口域で計9回の採集により得たものである。本研究で取扱った魚は、背鰭条数12~13、臀鰭条数25~27、胸鰭条数14~17、雄の臀鰭鱗数17~18、下顎歯数11~16、口蓋歯数7~11と計測されたので、Salangichthys microdon BLEEKER と同定された。体長組成の研究結果よりみて、雄の方が体長が大きい。すなわち雄の体長範囲は61.5~85.3mm、雌のそれは61.5~79.5mm、また、平均体長は雄で78.6mm、雌では73.7mmである。また雄の体長のモードは74~76mm、雌のそれは68~70mmであった。また、体長の頻度分布をみれば、雌雄ともに単一のモードを構成し、同一年齢群であると考えられる。体長(L)-体重(W)関係をあらわす場合、雌雄はそれぞれ次式であらわされる。雄:log W=3.00 log L-5.31 (r=0.90) 雌:log W=3.03 log L-5.44 (r=0.87) 肥満度の時期的変化をみてみると、雄では4.67~5.22、雌では3.57~4.48の間で変化し、雄の方がやや大きい値を示した。生殖腺指数の平均値は雄では0.124~0.252、雌では6.21~15.17であり、その時期的変化には特徴ある傾向は認められなかった。各時期別の卵の平均長径は0.75~0.93mmであり、2月19日の場合を例外として、終漁期に向ってやや下降する傾向がある。卵巣内の卵数は153~2,040で、大きく変化し個体による差が大きい。また孕卵数と体長、体重との相関関係は認められなかった。産卵期のシラウオの摂飼活動は、その消化管内容物の種類と量よりみて、不活潑であるといえよう。また捕食された餌料生物中では海産橈脚類の Calanus sinicus が卓越していた。この種は11月から2月にかけて長良川河口水域の塩分の濃い低層水中に多数分布することが知られている。

著者

木村 清志 中村 行延 有瀧 真人 木村 文子 森 浩一郎 鈴木 清 Kimura Seishi Nakamura Yukinobu Aritaki Masato Kimura Fumiko Mori Koichiro Suzuki Kiyoshi

出版者

三重大学水産学部

雑誌

三重大学水産学部研究報告 (ISSN:02875772)

巻号頁・発行日

no.10, pp.p71-93, 1983-10

被引用文献数

3

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1980年4月から1982年5月までの期間に,三重県英虞湾湾口部のアマモ場で,ビームトロールにより魚類の採集を行い,このアマモ場の魚類相とその季節的変化について,次のような結果を得た。1. 採集された魚類は13目53料117種27,293個体であった。個体数はゴンズイ,ギンポ,アミメハギ,ハオコゼ,ヨウジウオ,アナハゼの順に多く,この6種で全体の8割程度を占める。 2.各魚種の出現状態から,これらを周年定住種,季節的定住種、偶発種に分け,さらにいくつかのグループ,サブグループに細分した。 3. 種数は夏から秋に増加し,冬に減少する。4. 個体数のピークは5,6月,8月,10,11月,1,2月の年4回みられ,これらほスジハゼ,アミメハギ,ハオコゼ,アナハゼ,アサヒアナハゼ,ゴンズイ,ギンポ,サビハゼ,カワハギなどの変動に起因している。 5. このアマモ場の魚類相は,ヨウジウオ,ハオコゼ,アミメハギの周年にわたる出現,冬から春のギンポ,アナハゼ,6月のサビハゼ,8月のゴンズイの大量出現,夏から秋にかけてのベラ料やヒメジ科魚類の多種にわたる出現によって特徴づけられる。このような魚類相は暖流外海性の特徴で,黒潮沿岸各地のアマモ場の魚類相と共通性が高い。しかし,一方でほそれぞれのアマモ場の魚類相には特異性もみられる。 6. ギンポの大量出現ほ伊勢湾周辺のアマモ場の特徴である。 7. 英虞湾湾口部のアマモ場では有用椎幼魚の出現比率が低い。したがって魚類生産に関する限り,このアマモ場の水産的価値は小さいと判断される。Fish fauna of the Zostera bed at the mouth of Ago Bay, Mie Prefecture were studied by monthly samplings with a small beam trawl from April 1980 to March 1981 and from June 1981 to May 1982. The results obtained are summarized as follows : 1 ) 27,293 individuals (13 orders, 53 families, 117 species ) were collected in the Zostera bed. Plotosus lineatus, Enedrias nebulosus, Rudarius ercodes, Hypodytes rubripinnis, Syngnathus schlegeli,and Pseudoblennius percoides were dominant species. About 80 percent of the specimens collected belonged to these six species. 2 ) Each species of fish collected was divided into three categories, i. e. residents, seasonal residents, and casual species. Residents and seasonal residents were subdivided into a few of groups and subgroups as follows : (I) Residents ; fishes appearing in the Zostera bed all the year round. Group A ; fishes residing during the major part of their life cycle, and using the Zostera bed as their nursery, feeding and spawning grounds. Group B ; fishes inhabiting mainly during juvenile stage, and using the Zostera bed principally as a nursery ground. Group C ; fishes inhabiting chiefly during adult and subadult stages, and using the Zostera bed primarily as a feeding ground. Group D ; fishes universally distributed in the bay and commonly appearing in the Zostera bed. Group E ; fishes which may reside during all seasons in a very small number in the Zostera bed. (II) Seasonal residents ; fishes which spend a certain definite season in the Zostera bed. Group F ; fishes residing during juvenile and young stages and using the Zostera bed only as a nursery ground. Subgroup a ; fishes which spend a long perid of time ( more than four months) in the Zostera bed. Subgroup b ; fishes which spend a short period of time ( less than three months) in the Zostera bed. Group G ; fishes residing from juvenile to adult or subadult stages. Subgroup c ; fishes which inhabit the Zostera bed in a large number, and which use the Zostera bed as nursery, feeding, and spawning grounds. Subgroup d ; fishes which reside in the Zostera bed principally as a nursery ground. (III) Casual species ; fishes appearing casually in the Zostera bed. 3 ) Number of species increased from summer to autumn by recruitment of juveniles belonging to seasonal residents and casual species, and then decreased in winter. 4 ) Total number of individuals increased in May or June, August, October or November, and January or February. This fluctuation was caused by seasonal changes of populations of the following nine species ; Acentrogobius pflaumi, Rudarius ercodes, Hypodytes rubripinnis, Pseudoblennius percoides, P. cottoides, Plotosus lineatus, Enedrias nebulosus, Sagamia geneionema, and Stephanolepis cirrhifer. 5 ) The fish fauna of the Zostera bed at the mouth of Ago Bay was chracterized by the following : ( 1 ) Syngnathus schlegeli, Hypodytes rubripinnis, and Rudarius ercodes residing all year round. ( 2 ) Appearance in great number of Enedrias nebulosus and Pseudoblennius percoides from winter to spring, of Sagamia geneionema in June, and of Plotosus lineatus in August. ( 3 ) Subsistence of many species of fishes belonging to Labridae and Mullidae from summer to autumn. 6 ) Appearance of Enedrias nebulosus in large number was a peculiar feature of the fish fauna of the Zostera bed in and around Ise Bay, central Japan. 7 ) As far as the fish production in concerned, the Zostera bed at the mouth of Ago Bay had little significance for inshore fishery because there the juveniles of useful fishes were very few.