本研究從民國81年 2月至82年 4月, 探討哈盆溪之臺灣馬口魚
(Zacco barbata) 其族群結構, 兩性差異, 對於棲地的利用, 以及
族群數量及族群密度的變化等。
經過一年多在哈盆溪以電魚法的魚隻收集發現, 臺灣馬口魚的
雌雄比例與 1： 1並無顯著差異, 每個月所捕捉的臺灣馬口魚中,
不同體長群的比例之間有顯著差異。體型較大的臺灣馬口魚可由第
二性徵分辨其性別, 第二性徵包括頭部及臀鰭上的追星與體側的婚
姻色。兩性體型較大的個體其頭部的追星及體側的婚姻色終年可見
, 雄魚比雌魚明顯, 只友有在生殖季時才能在成熟雄魚的臀鰭上發
現追星, 雌魚則終年皆未發現。
由每個月卵徑頻度分佈, 成熟度指標 ( GSI, gonadosomatic
Index), 及生殖腺發育狀態發現, 民國81年哈盆溪的臺灣馬口魚其生
殖季為 4- 10月, 且為多次產卵。82年的生殖季則至 4月尚未開始
。兩性的體型有顯著差異, 雄魚的平均體長較雌魚為大。其中生殖
腺已達性成熟狀態的雄魚, 其平均體長亦較雌魚為大。所發現已達
性成熟的最小雌魚及雄魚分別為79mm與75mm, 雌魚於長至 110mm以
上生殖腺完全達到性成熟狀態, 而雄魚長至 130mm時仍有 8％未達
性成熟。因此, 大部份雄魚要比雄魚長至較大體長才達到性成熟狀
態。體型較大的雌魚其孕卵數較多, 但是卵徑並不會比較大。體型
較小的雌魚貢獻在生殖方面能量的比例不會比較少。因此, 可能由
於生殖策略不同而造成兩性體型的差異。
由棲地因子分析結果顯示, 臺灣馬口魚適宜的棲地為水流較緩
, 兩岸靠水處有草叢可以隱藏, 底質石較小, 水底未被泥沙淤積的
水域。夏季的族群數量及族群密度皆較冬季為高。四個研究站的族
群數量也有顯著差異。

The research was conducted in Ha-Pen Nature Reserve
from Feburary, 1992 to April, 1993. The purpose of this
study is to investigate the population structure, sexual
differences, habitat use, and reproduction biology of
Zacco barbata, an endemic freshwater fish of Taiwan.
After more than one year survey, the result showed
that the sex ratio of Zacco barbata was significatly
different from 1: 1. The sexual dimorphism in larger Zacco
barbata could be distinguished by their secondary sexual
characters, which include the pearl organs locating on
heads and anal fins, and the breeding color on their
lateral sides. Generally speaking, males are larger than
females in average total length. However, the smallest
sexually mature males and females are 75 mm and 79 mm,
respectively.
From GSI (gonadosomatic index) data, development of
gonads and distribution frequencies of egg diameter, we
found out that the breeding season of Zacco barbata in
Ha-Pen Creek was from April to October in 1992, and the
peak of breeding season from April to July. Based on the
development of eggs in ovary, we could tell that females
of Z. Barbata have multiple spawning.
Female with longer total length usually had
heavier ovary is due to containing more eggs instead of
bigger eggs. We suspected that the relative energy input
to the breeding effort in smaller females were about the
same as that of larger ones.
The suitable habitat for Zacco barbata was stream
with low velocity, where had good vegetation coverage on
both sides for hideouts, and the sediment is minimal. The
population density varied with seasons, higher in summer
than in winter. There were also significant difference in
population size among the four study stations.
The research was conducted in Ha-Pen Nature Reserve