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Effects of Temperature and Salinity on Larval Development of the Freshwater Shrimp Macrobrachium Nipponense
溫度及鹽度對日本沼蝦(Macrobrachium nipponense)幼苗發生之影響
摘要
鬼頭刀胃內含物之取材是從1985年4月至1987年6月在東港及新港魚市場所測定之4,198尾，其中包括幼魚及成魚，其研究結果如下：鬼頭刀之空胃率高，平均32％（雄35％，雌30％)。兩海域雌雄間食性經x^(2)檢定結果無差異，但兩性間季節性變化仍有顯著差異。在20 cm以下之幼魚，其胃含物主要為海藻及浮游生物；20 cm以上則攝食範圍較廣，魚類75％，蝦類18％，頭足類16％。甲殼類之被食率隨魚體長而下降，頭足類則維持穩定狀態，魚類則隨鬼頭刀體長增大而上升。鬼頭刀所攝食之魚類，其體長多在25 cm以下，其主要魚種為日本鮆24％、鰺20％、飛魚14％、眼眶魚8.4％，其所攝食之魚體都在中型以下。鬼頭刀之飽滿度，0～4.8％（平均3.5％）：體長20～50 cm者飽滿度為1.0％以下，50～75 cm者為3.0～4.8％，為飽滿度之最高峰。鬼頭刀食餌構成，每年每月所攝食的魚種都有不同季節變化，且各季節所捕食之魚種無一定之規則可循。漁場所出現之稚魚種類大多和鬼頭刀攝食餌料相類似，由海域生物相觀察，鬼頭刀攝食範圍為海面至水深20公尺之處。
並列摘要
A total of 4,198 dolphin-fish including juveniles and adults collected fromTungkang and Hsinkang during April 1985 and June 1987,for the analysisof their stomach contents were stated below.Stomach content weight index(SCWI)increased seasionally from April to June and dropped down thereafter.The seasonal variation of SCWI of each food item,however,did not showany meanful regular pattern.A remarkable high frequency of empty stomach(34% of male and 30% of female in Hsinkang;and 38% of male and 32% offemale in Tungkang)were observed from both locations.The juvenile dolphinfishof smaller than 20cm fork length fed mainly on planktons including larvalfishes.As they grew larger than 20cm,they relied more on larger fishes(75%),shrimps(18%)and cephalopods(16%),when expressed in percentage frequenceof occurrence.Concering the fish item alone,Engraulis japonicus was the mostfrequent species with 24% and followed in the decreasing order of importanceby carangids(20%),exocoetids(14%),Auxis(12%)and Mene maculata(8.4%).