台灣西南部七股溪河口魚類生物量與棲地利用之研究

Abstract

台灣西南部七股溪河口沿岸遍佈紅樹林，且處於感潮河段，擁有豐富生物資源，許多漁民架設的網笱(定置網)，是本區常見的漁具類型，本研究在2008年11月至2009年10月間在七股溪河口地區選取三測站，以網笱為採樣工具，分析每月漁獲物，主要目的為探討七股地區的魚類生物量、生物多樣性及魚類棲地利用。結果顯示，研究期間共計採獲魚類1,975尾，分別屬於34科49屬63種，這些魚隻體型大多偏小，體長分佈多數在1-20cm內，佔總捕獲尾數的(93%)；體重多數分佈在1-60g內，佔總捕獲尾數約(90%)。全年魚類推估生物量則是以潟湖地區最高，交會口測點次之、七股溪測點最少。此外，位於河道地區的七股溪測點與交會口測點，兩者在魚類推估生物量及月別變動趨勢上較為相近，但七股潟湖測點則不同，又三測點在8-11月皆有明顯的峰型表現。由五個生物多樣性指數來看，呈現種豐度高，多樣性高，並非針對特定魚種進行漁獲。以魚類河口棲地利用而言，可將七股溪魚類分為四群，及具有生長潛力的海洋型19種，逢機大量發生型5種，經常利用型16種及偶發出現型23種。在漁業資源的利用與管理上，逢機大量發生型可以利用，河口經常利用型魚類可部分利用，而生長潛能較大的海洋型及偶發型魚類不宜利用。

Cigu estuary located at southwestern Taiwan, formed by mangrove sandbar, with rich in biological resources. Many fyke nets surrounding estuary and lagoon area were set up by local fishermen. The main purpose of this study is to estimate local fyke net fishery resources ,fish biodiversity, fish guilds construction and offer fishery management suggestion. The study sampling was carried out from November, 2008 to October, 2009. Three fyke net sampling sites was randomly chosen, data was collected monthly. The results showed total 1975 individuals was sampled, belonging to 34 families 49 genera 63 species. About 93% of total individuals the length frequency is located in the scale 1-20cm, and nearly 90% of all individuals the weight is below 60g. Most of smapling fishes are smaller size. Cigu site and cross site have closely fishery estimated resources and variation transcend, the other lagoon site is differ from them. But three sites have a higher peak performance during August to November. The year estimated fishery resource have highest performance in lagoon site, followed by intersection site, and Chigu River site at least. Five Biological diversity index was used to describe the fish data. Showing a higher value in species richness index indicating that fyke net, not to catch a specific species; diversity index is higher, indicating fyke net can catch various of fish species. Finally, the homogeneity index is higher, said the fyke net catch is not focus on dominant species. In other words, Cigu River estuary fyke net catch, not for a particular species, but various of species. In this study, the concept of guilds was used to separate all the fish species.All species was divided into four groups: straggler (S) type up to 23 species, followed by marine (M) type 19 species, estuary common (E) type 16 species,and the least occational opportunity (O) type 5 species. The advise of fyke net fishery resource management can be divided into three groups: availability of fishery resources occational opportunity guild. Partually use of fishery resources estuarine common fish guild and marine guild. Non-fishery resource is straggler guild.