| Summary: | 碩士 === 國立臺灣大學 === 漁業科學研究所 === 99 === Fish will change with and increases along with the environmental condition, the community fades and the age structure. Research in fish’s age structure, sex ratio, density, the sphere of action as well as the environment factor influence are called the ecology population. Nanzaigou stream was located at the tributaries of Shihmen Reservoir, it was often over-flooded and caused serious damage along the stream side, so it was restored by the natural ecological engineering from March 2004 to November 2006. The study intends to explore the differences of the dominant species Zacco barbata population before, during and after restoration at each site in Nanzaigou Stream, as well as the age structure and reproductive cycle of this species. Sampling was conducted along the stream from Baiji NO.4 Bridge, Nanzihgou NO.2 Bridge, Longxing Bridge, Fengyi Bridge, Sinfu Canal and Huaide Bridge by electrofishing from November 2003 to November 2010. And the mean values of dominant species densities, body length, body weight and condition factor were compared by one-way ANOVA. And used scales to assessment the age and growth of the dominant species were capture of the same sites by Shrimp cage and electrofishing from September 2009 to November 2010. The results were as follows. The density mean value in Long Xingqiao is biggest (7.00/15min), but the fork length and body weight were small, extrapolated that maybe the Evades the fish grid and Ecology island has provided reason of the asylum to the juvenile fish. The first phase of construction with the typhoon, the densities of fish each site declined, so has the typhoon to be enormous to the construction measuring point to the fish density influence. The mean value of body length and weight were biggest at Fengyi Bridge, extrapolated that maybe the construction labor law to the adult fish is of help.Comprehensive result, when Nanzaigou stream carries on the restoration there has not caused the enormous damage on the mean value of density, body length, body weight and condition factor for Zacco barbata, But it will need the following longer-term environment inquiry material discussion to the population of Zacco barbata after construction in Nanzaigou stream. A total of 192 individuals were captured to use scales to assessment the age and growth of the dominant species. The range of fork length was 2.9-17.0 cm, the highest rings were counted to 3. The rate of marginal increment was highest from July to September, and which indicated that one ring was formed yearly. The age composition respectively was 0 year old of fish 23.4%, 1 year old of fish 24.7%, 2 year old of fish 41.8% and 3 year old of fish 10.1%. The population in Nanzaigou stream faced with typhoon caused disaster and ecological engineering causes population density to reduce, the body weight and the condition factor is small, as well as the species food competition pressure high, causes it to choose r-selection the survival strategy, the age structure to shift to an earlier time the mature low age fish primarily.In the future regarding the species’ care and the cicada chrysalis, which should place the environment improvement with emphasis, maintains the good water quality and suitable to perch roosts the environment, will be helpful in the population restores.
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