台灣南部高屏溪及菲律賓阿部羅格溪烏魚棲地利用及生活史策略之 比較

Abstract

為了瞭解烏魚生活史策略及棲地利用，2007年11月至2008年2月總共在台灣的高屏溪河口採集了578尾烏魚，另外亦於菲律賓西北部的 Abulog 河口採集了9尾烏魚。其中有136尾用於年齡判定、42尾利用電子微探儀進行耳石鍶鈣比的分析。高屏溪河口補獲的烏魚之平均(±SE)尾叉長為 420.47 mm ± 2.43，年齡約2歲。體長體重關係之分析結果顯示此區的烏魚呈現等速成長現象(isometric growth)。首次成熟之尾叉長估計約 315 mm。成長參數以范氏成長方程式(von Bertalanffy growth equation)計算結果顯示極限尾叉長為 568.40 mm，成長係數(growth coefficient)為 0.22。生殖腺指數(Gonadosomatic indices)顯示烏魚的產卵期為冬天。耳石鍶鈣比的時間序列變化顯示高屏溪大部分的烏魚皆為淡水和海水之間的河口域洄游型。然而，菲律賓北部的烏魚則大部份時間是待在淡水溪流中。此結果顯示烏魚的棲地選擇的不確定性，可能依當地棲地的環境狀況而定。

To understand the habitat use and life history strategies of the grey mullet Mugil cephalus, a total of 578 and 9 individuals were collected respectively from Kao Ping River in southwest Taiwan and from Abulog River, northwest Philippines in November 2007 to February 2009. Among them 136 individuals were aged by reading the annulus in the whole otoliths and 42 individuals were analyzed for otolith strontium to calcium ratios by electron probe microanalyzer. The mean (±SE) fork length (FL) of the grey mullet collected from Kao Ping River estuary was 420.47 mm ± 2.43, corresponding to an age of 2+ years. The relative growth of weight on length of the grey mullet was isometric. The length at first maturity was estimated to be 315.00 mm in fork length. Growth parameters of the mullet was fitted by von Bertalanffy growth equation as: asymptotic length (L∞) = 568.40 mm FL an growth coefficient (K) of 0.22. Gonadosomatic indices indicated that the mullet spawned during the winter season around December. The temporal change of Sr:Ca ratios in otolith indicated that most of the mullet from Kao Ping River was estuarine contingent. However, the Mugil cephalus from northern Philippines stayed longer in freshwater. These results indicated that the habitat use of the grey mullet is facultative, which depends on the environmental availability.