金門南方海域產黃鯽之刺網選擇性對成長參數估計的影響

Abstract

本報告以脊椎骨輪紋判讀法，估計金門南方海域產黃鯽(Setipinna taty)之年齡，並應用非線性迴歸法估計von Bertalanffy體長成長方程式。再以修飾Holt (1963)法估計刺網之網目選擇性，並探討選擇性對成長參數估計的影響。結果如下： 1．樣本魚之尾叉長介於8.1-17.8cm間，呈雙峰分佈，主型量位於15.25cm，次型量位於12.25cm。 2．脊椎骨一年形成一輪，形成時期大約在冬季至春季間。 3. von Bertalanffy體長(cm)成長方程式為 L(下標 t)=23.45 (l-e [-0.40(t+0.37)] 4. 4.00cm (A), 4.29cm (B)，及5.00cm (C)三種網目之最適選擇體長(lm)及選擇因數(k)分別如下： (a)尾叉長>=14.0cm樣本魚之(下標 A)l(下標 m)＝14.8cm, (下標 B)l(下標 m)＝15.5cm, (下標 C)l(下標 m)＝15.8cm及K(下標 A)＝3.71,K(下標 B)＝3.62，K(下標 C)=3.17 (b)尾叉長＜14.0cm 樣本魚之(下標 A)l(下標 m)＝11.7cm, (下標 B)l(下標 m)＝11.4cm, (下標 C)l(下標 m)＝12.3cm及K(下標 A)＝2.94,K(下標 B)＝2.66，K(下標 C)=2.46 5．在漁獲物以刺入方式被捕獲的情況下，有網目越大，最適選擇體長也越大的關係；而在纏絡的罹網方式下，網目與最適選擇體長間的關係則較不明顯。 6．刺網之網目選擇性，會影響成長參數的估計。

The age of Setipinna taty in the southern Kinmen waters was determined by vertebral ring-count, and its von Bertalanffy's growth equation was estimated by nonlinear regression. Furthermore, the mesh selectivity of gill net was estimated by modified Holt's method (1963), and used to discuss the influences on the estimation of growth parameters. The results were as follows: 1. Observed length frequency distribution ranged from 8.1 to 17.8cm as well as it showed bimodal. The main mode was at 15.25cm, and the second at 12.25cm. 2. The annulus of vertebrae was formed annually, and the period was between winter and spring. 3. The von Bertalanffy's equation of fork length (cm) was estimated L(subscrip t)=23.45 (1-e (-0.40(t+0.37)) 4. The optimum selection lengths (lm) and selection factors (k) of three meshes, i.e., 4.00cm(A), 4.29cm(B), and 5.00cm(C) were as follows: (a) When fork length of specimens >=14.0cm, (subscrip A)l(subscrip m)=14.8cm, (subscrip B)l(subscrip m)=15.5cm, (subscrip C)l(subscrip m)=15.8cm, and k(subscrip A)=3.71, k(subscrip B)=3.62, k(subscrip C)=3.17. (b) When fork length of specimens <14.0cm: (subscrip A)l(subscrip m)=11.7cm, (subscrip B)l(subscrip m)=11.4cm, (subscrip C)l(subscrip m)=12.3cm, and k(subscrip A)=2.94, k(subscrip B)=2.66, k(subscrip C)=2.46. 5. The optimum selection length increased with mesh sizes when specimens were caught by the wedged pattern, but it didn’t showed same trend when specimens were caught by the tangled pattern. 6. The mesh selectivity of gill net indeed affects the estimation of growth parameters.