Age and Growth of the Moon Fish, Mene maculata, before and after Heavy Exploitation in Southwestern Taiwan Waters

Abstract

近年來台灣西南海域皮刀魚(Mene maculata)的漁獲量明顯減少，為了要瞭解漁撈對其年齡結構及成長的影響，本研究利用在1981~1984年及1995~1997年兩段時間所測量的體長頻度資料以多體長頻度分析軟體MULTIFAN分析。范式成長方程式估計如下：1981~1984年：L(下標 ∞)=279.8mm，K=0.186/yr，t(下標 o)=-1.7yr，3個年齡群平均體長分別為110.5mm，139.2mm及163.1mm，1995~1997年：L(下標 ∞)=218.5mm，K=0.285/yr，to=-1.34yr，4個年齡群平均體長分別為106.3mm，134.2mm，155.1mm及170.8mm。Hotelling檢定結果顯示此兩段期間皮刀魚的成長有顯著差異。1995~1997年間皮刀魚有較小的極限體長及較快的成長率，此可能是因漁獲壓力增加造成密度相依成長而產生的調適。The catch of moon fish, Mene maculata, from the southwestern waters off Taiwan declined significantly in recent years. In order to examine the effect of exploitation on growth and age structure of moon fish, two length frequency data sets during the two periods 1981-1984 and 1995-1997 were analyzed with multiple length frequency analysis (MULTIFAN). The parameters of von Bertalanffy growth equation (VBGE) estimated by MULTIFAN were as followings: 1981-1984: asymptotic standard length L(subscript ∞)=279.8 mm, growth rate K=0.186/yr, t(subscript o)=-1.7 yr, three age classes were identified and mean length was 110.5 mm, 139.2 mm, and 163.1 mm for ages 1-3, respectively. For 1995-1997 period, L(subscript∞)=218.5 mm, K=0.285/yr, t(subscript o)=-1.34 yr, four age classes were identified and mean length was 106.3 mm, 134.2 mm, 155.1 mm and 170.8 mm f or ages 1-4, respectively. Significant difference on the VBGE between the two periods was found with Hotelling's test. Smaller asymptotic length and faster growth rate of the 1995-1997 period suggested that the moon fish compensate the effect of increasing of fishing effort through a density-dependent growth.