哈盆溪臺灣馬口魚（Zacco barbata）之生殖生態

Abstract

This research was conducted in Ha-Pen Nature Reserve from February, 1992 to April, 1993. The purpose of this study is to investigate the population structure, sexual differences and reproductive biology of Zacco barbata, an endemic freshwater fish of Taiwan, in Ha-Pen Creek.After more than one year survey, the result showed that the sex ratio of Z. barbata was not significantly different from 1:1. The sexual dimorphism can be distinguished in mature individuals by their secondary sexual characters, which include the pearl organs, locating on the head and anal fins, and the breeding color on lateral sides. Generally speaking, males were larger than females in the average total length. The smallest sexually mature females and males investigated, were 79 mm and 75 mm, respectively.From GSI (gonadosomatic index) data, gonad development and egg diameter, we found out that the breeding season of Z. barbata in Ha-Pen Creek was from April to October in 1992, and the peak of breeding season was from April to July. Based on the development of eggs in ovary, we discovered that females of Z. barbata have multiple spawning.Females with longer total length usually had heavier ovaries, due to containing more eggs instead of bigger eggs. We suspected that the relative energy input to the breeding efforts in smaller females were about the same as that of larger ones. The breeding strategy taken by Z. barbata was discussed in the report.