Growth and reproductive biology of the four finger threadfin, Eleutheronema tetradactylum (Shaw), in an aquaculture pond, Pingtung, Taiwan.

Abstract

The growth performance and reproductive biology of farmed four finger threadfin, Eleutheronema tetradactylum, were analyzed in this study. Four finger threadfin were able to grow to ＞300 g after 8 months of rearing, and began to breed after 10 months of rearing. The gonadosomatic index and histological analysis of the gonads clearly showed that the breeding period of farmed four finger threadfin is from February to September. The four finger threadfin is considered to be a protandrous hermaphrodite based on results of histological observations, and size distributions of male, female, and bisexual individuals. In addition, females increased from 34.55% in 1+ aged fish to 90.32% in 3+ aged fish. All oocyte development stages presented in an ovary indicated that the four finger threadfin is an asynchronous fish that is relevant to farm observations that fish spawn 2~3 days after every full-moon spring tide during the reproductive period. Observation of fecundity revealed that berried females (25.7~50.3 cm) of the four finger threadfin carried about 3.17×10^5~25.08×10^5 eggs, and the fecundity of females increased with increases in the size and ovary weight of females.本研究在分析養殖四絲馬鮁的成長及其生殖生物學。養殖四絲馬鮁可在8個月長至300公克以上，且於養殖10月後開始生殖。生殖腺指數及生殖腺組織學分析清楚顯示臺灣養殖四絲馬鮁的生殖季介在每年2月至9月期間。根據公母魚體型分佈及兩性個體的發現，可知四絲馬鮁屬於雄性先熟的雌雄同體，其母魚比率會隨年齡增加，由1齡魚的34.55%增加至3齡魚的90.32%。組織學分析亦顯示，四絲馬鮁魚的卵巢為非同步成熟，因為所有發育階段的卵細胞可發現存在同一卵巢中，這與生殖季期間，每當滿月大潮後，母魚都會產卵2－3天的發現是一致的。生殖力分析結果顯示，每尾母魚（25.7～50.3 cm）卵巢中的卵數約為3.17×10^5～25.08×10^5 eggs，且其生殖力會隨母魚的體型及卵巢的重量提高而增加。