Estimation of the Biomass of Larval Anchovy Along the Coastal Waters of Fang-Liao by Hydroacoustic Method

馬鮁魚科在本省西南海域，已知二屬四種，一爲四絲馬鮁屬(Eleutheronema)，二爲馬鮁魚屬(Polynemus)，本種是屬馬鮁魚科屬中較大的一種，體長可達60 cm。本研究以1990年8月至1992年7月間在本省西南海域所捕之五絲馬鲅共658尾，此魚乃爲先雄後雌之性轉變的魚種，其尾叉長在25 cm以下者全部雄性，爾後轉變雌雄同體（其尾叉長爲20～40 cm之間）。雌雄同體階段之精巢先熟，交尾後有75％轉換爲雌性，其餘25％則無性轉换，由卵徑組成及生殖腺指數推定結果其產卵爲6～8月，產卵次數最少兩次以上，其抱卵數爲18.4×10^(5)－36.6×10^(5)，依體長而異。五絲馬鮁依鱗片檢視結果爲一年一輪，其年齡判定係依據一年一輪爲基準，一歲魚爲125.8 mm，二歲魚爲182.3 mm，三歲魚爲228.4 mm，其漸近體長702.5 mm，成長曲線如下：L(下标 t)=702.5[1-e(上标 -0.093(t+1.23))]W(下标 t)=5.78×10^(3)[1-e(上标 -0.093(t+1.23))]^(2.89)有關馬鮁魚之食性，15 cm以下時，乃以蝦類爲主，多毛類次之。長成則以魚類居多，烏賊類次之。在兩性期其食物量較少，最多爲雌性成熟期。其次雄性成熟期，其食性乃依性之轉變而異。

關鍵字

超音波探測；鮆科稚魚；魚群量評估

並列摘要

The common striped threadfin Polydactylus plebejus is a demersal fish dwellingon sand or mud bottoms frequently in turbid shallow water.It is one of themost important commercial fishes in Taiwan.Breeding season of stripedthreadfin ranges from June to August.Absolute fecundity varies from 1.84 to3.66 million depending on body size.The sex reversal takes place at the sizeof 30 to 45 cm in fork lengh.This species has a remarkable characteristics ingonad structure which exhibits hermaphroditic transitional prodandrous duringits life cycle.The relationships between fork length(L)and body weight(W)is not different between sexes and can be expressed as W(subscript t)=3.43×10^(-5)L^(2.89).Theannual ring on the scale is formed approximately during June to August in thereproduction season.The growth equation is obtained as:L(subscript t)=702.5(1-e(superscript -0.093(t+1.23)))orW(subscript t)=5.78×10^(3)(1-e(superscript -0.093(t+1.23)))^(2.89)The fish feeds mainly on benthic shrimps(38%),fishes(26%),small crabs andlobsters(16%),polychaetes(10%),squids(5%),and other undetermined items(7%).Fishes are consumed more by larger female threadfins while smallershrimps and polychaeta are eaten primarily by smaller male threadfins andsquids are more taken frequently in hermaphroditic threadfins.

並列關鍵字

Hydroacoustic Survey ； Larval Anchovy ； Biomass Estimation

國際替代計量

Estimation of the Biomass of Larval Anchovy Along the Coastal Waters of Fang-Liao by Hydroacoustic Method

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