台灣東部沿岸三種鶴鱵（扁鶴鱵、叉尾鶴鱵及鱷形叉尾鶴鱵）之體長與生殖參數研究

Body lengths and Reproductive Parameters of Three Needlefishes, ＂Ablennes hians, Tylosurus Acus Melanotus, and T. crocodiles Crocodilus＂, in Coastal Waters of Eastern Taiwan

扁鶴鱵、叉尾鶴鱵及鱷形叉尾鶴鱵均為溫、熱帶海域表層洄游之鶴鱵科魚類。本研究於2009年2月至2010年6月間，於台灣東部七星潭與石梯坪海域，利用定置網採集該3種魚類樣本。為了還原因長吻易斷而無法測量之標準體長，本研究建立此3種鶴鱵軀幹長與標準體長關係式，而此關係式不受性別與採集水域之影響。扁鶴鱵、叉尾鶴鱵及鱷形叉尾鶴鱵上下頜均完整而可測量標準體長之樣本，占本研究該種總樣本比例，分別為36.11、53.07及91.30%，還原後標準體長範圍分別為47.5-89.9、53.3-88.9、43.3-116.6 cm。該3種鶴鱵雌魚之平均標準體長均大於雄魚。本研究亦估算此3種鶴鱵之體長與體重關係式，而此等關係式會因魚種之不同而出現性別與採集水域影響之差異。叉尾鶴鱵生殖腺指數（GSI）、肝體指數（HSI）和肥滿度（CF）等生殖參數會受到性別和/或採樣區之顯著影響，但是扁鶴鱵與鱷形叉尾鶴鱵則否。由GSI、HSI及CF之月別變化來推測，叉尾鶴鱵在台灣東部沿岸之生殖季至少在4月到6月，扁鶴鱵至少在2月到5月，惟鱷形叉尾鶴鱵因樣本過少而無法判定。性比（SR）在扁鶴鱵顯著較高（58.5%），然而叉尾鶴鱵（41.3%）與鱷形叉尾鶴鱵（39.6%）則均較低，但僅前者達顯著水準。雖然如此，此3種鶴鱵之性比均有隨體長之增加而有增高的現象發生。

Flat needlefish, ＂Ablennes hians＂, keel-jawed needle fish, ＂Tylosurus acus melanotus＂, and hound needlefish, ＂T. crocodilus crocodiles＂, are common migratory pelagic Belonidae fish in the temperate and tropical waters. These three needlefishes were collected from February 2009 to June 2010 using set nets in coastal waters of Chishingtan and Shihtiping in eastern Taiwan. Relationships between body lengths and standard lengths (SLs) were investigated in this study because SLs are often unmeasurable due to the fish’s long slender jaw that can easily break during capture. The relationship was unaffected by gender and habitat waters. Percentages of ＂A. hians＂, ＂T. acus melanotus＂, and ＂T. crocodilus crocodiles＂ individuals with complete long slender jaws and SLs measured in the samples of this study were 36.11, 53.07, and 91.30 %, respectively. Ranges of the estimated SLs for these three needlefishes were 47.5-89.9, 53.3-88.9, and 43.3-116.6 cm, respectively. Mean SLs of females were larger than those of males for all three needlefishes. Relationships between SL and body weight (BW) were estimated, and the effects of gender and habitat waters significantly varied among species. As to the reproductive parameters, the gonadosomatic index (GSI), hepatosomatic index (HSI), and condition factor (CF) were significantly affected by gender and/or habitat waters for T. acus melanotus but not for ＂A. hiansand T. crocodilus crocodiles＂. From the monthly variations of the GSI, HSI and CF, the reproductive season was estimated at least from April to June for ＂T. acus melanotus＂, at least from February to May for ＂A. hians＂, but was not clear for ＂T. crocodilus crocodilusdue＂ to insufficient samples. The sex ratio (SR) was significantly higher in ＂A. hians＂ (58.5 %), but lower in ＂T. acus melanotus＂ (41.3 %) and ＂T. crocodilus crocodilus＂ (39.6 %),and only that of ＂T. acus melanotus＂ reached significance. However, SR was found to increase with SL in all three needlefishes.