Investigation On Present Situation Of Fishery Resources And Their Development And Utilization In Nanwan Reservoir, Henan Province

This paper took Nanwan Reservoir in Henan Province as its research object, an investigation on physiochemical features of water quality and bait biological changes were conducted in Nanwan Reservoir from 2004 to 2005. On the basis of these investigations the trophic type and present situation of fishery resources were evaluated in order to provide theoretical base for the reasonable utilization of fishery resource and ecological management of environment. The main results obtained were as follows:1. The average water temperature was 17.8℃ in Nanwan reservoir. The average secchi degree of water body was 2.4m; the changing range of pH was 6.60-8.04; the average content of DO was 7.5mg/L; the mean concentration of TN was 0.33mg/L; the mean concentration of TP was 0.049mg/L. So the water quality of Nanwan reservoir was subordinated to medium trophic type.2. There were 144 species of phytoplankton belonging to 89 genuses of 7 phyla. The average density was 2.06×10⁵ ind./L in a year, and the mean biomass was 0.32mg/L. Phytoplankton was dominated by diatom and blue algae according to density. Biomass was dominated by diatom. The fish productivity of silver carp and bighead carp was 1.19×10⁶ kg in Nanwan reservoir based on the measurement of the elementary productivity of water body.3. There were 32 genuses (species) of zooplankton, the average density and biomass of zooplankton were 560 ind./L and 3.28mg/L, respectively. There were 3 species of macrozoobenthos, the mean density and biomass of zoobenthos were 263.83 ind./m² and 0.60g/m², respectively. Periphtytic algae belonged to bacillariophyta, cyanophyta and chlorophyta. The average biomass of periphtytic algae were 0.089mg/m³.4. There were 37 species of fish belonging to 31 genuses of 11 families of 6 orders in Nanwan reservoir. The growth feature of Erythrocrlter ilishaeformis and Aristichthys nobilis were analyzed. The regression relationship function between body weight (W) and body length (L) were W=0.0489 L^2.7274 (r²=0.9793) and W=0.0413 L^2.8472 (r²=0.9422) for E. ilishaeformis and A. nobilis, respectively. Their growth inflexion age were 6.7a and 7.46a, respectively.5. According to present situation of fishery resources in Nanwan reservoir, it was suggested that the stocking of zooplankton carp should be strengthened, brand of "nanwanyu" should be developed, and some management methods should be carried out to protect the fish resources and water environment. These methods will help to keep a sustainable development of fisheries in Nanwan reservoir.