Studies On Age Structure And Diversity Of Fish Community In The Niushan Lake

Age structure and diversity of fish community in the Niushan Lake were studied. An investigation was taken on the status of fishery resource in order to optimize fish community structure and protect fishery resource. Scales were used for age determination and a modified seine was used for collecting samples to study diversity of fish community. Main results were as follows.1. A total of 35 species were collected, which could be classified into 11 families, 23 species belonging to Cyprinidae, 2 species to Serranidae and 2 species to Eleotridae, and only one species to each of the remaining 8 families. It is showed that Fish species diversity had decreased in recent decades.2. The small fishes, including C. auratus, C. erythropterus, H. leucisculus, P. parva, T. swinhonis and H. swinhonis, were abundant in the catch. P. parva and T. swinhonis had only one age class. The population of A. rivularis and S. nigripinnis had two age classes and most of them were one year old. The age structures of C. auratus, S. chuatsi, C. alburnus and C. erythropterus were mainly consisted of 1~3 age classes. C. auratus, C. alburnus and C, erythropterus grew slowly in the Niushan Lake.3. The growth of C. alburnus and C. erythropterus were studied. The growth equations were as follows:4. Seine was one of the best sample methods for studying fish community. A total of 19 species, including 7877 individuals, were collected in the Niushan Lake. C. erythropterus, S. nigripinnis, A. rivularis, P. parva, H. leucisculus, T. swinhonis and H. swinhonisb were abundant. Age structures of fishes were mainly 1 age class in the seine. P. parva, T. swinhonis, C. erythropterus and Acheilognathinae, including R. ocellatus, R. lighti and P. imberbis, were the numerically dominant species.5. Fish community composition was different among the sampling areas of Niushan Lake. Small fishes, mainly Acheilognathinae, were the most abundant in the centre area. The other areas were mainly C. erythropterus and T. swinhonis.6. Macrophyte played important role in the distribution of fish community. Biomass of fishes in the macrophyte regions was significantly higher than in the regions without macrophyte. There was no significant effect of depth and transparenceon the distribution of fish community in the Niushan Lake. The density of fishes in the seine was about 2.5 ind'm-2 or 14 g'm-27. Diversity of fish community in the seine was low. Diversity index(H' ), dominance index( ) and evenness index(J' ) offish community were 1.279, 0.476, and 0.451 respectively.