Status And The Strategies For Rational Exploitation Of Reservoir Fisheries Resource In Jiangsu Province

During May 1998 to December 2001, the surveys on more than 40 indices such as geomorphology and physical environment, water physio-chemical quality, phytoplankton, primary productivity, zooplankton, benthic animals, macrophytes, and fish resources for 48 large- and middle-sized reservoirs in Jiangsu Province were carried out. The fisheries circumstances and aquatic biotic resources status were summarized systematically. The structures and functions of aquatic communities in reservoirs with different latitudes were comparatively studied. Classifications of trophic types and the evaluation of potential fishery yields for reservoirs were made. And hence the rational exploitation strategies for reservoir fisheries were put forth. It is of important roles and practical significances in forwarding reservoir fisheries along healthy and sustainable development. The main results are as follows:1. Water physio-chemical characteristicsThe means of physio-chemical indices for 48 reservoirs were shown as follows: transparency 109.8 cm, DO 8.02 mg/1, conductivity 244.8 u s/cm, pH 8.3, COD 4.2 mg/L, total alkalinity 75.2 mg/L, total hardness 105.4 mg/L, total nitrogen 1.06 mg/L, total phosphorus 0.206 mg/L. It was indicated that these indices measured were mostly within the favorable ranges for fishery (except very few indices), and the phosphorus usually as limiting factors in reservoirs were not deficient in the large and middle reservoirs in Jiangsu Province, but contrastingly, the total nitrogen were relatively lower.2. Status of aquatic biotic resources(1) Phytoplankton and the primary production7 phylum and 59 genera of phytoplankton in total were found. The dominant species were Microcystis sp, Phormidium sp, Synedra sp, Melosira sp, Cyclotella sp, Navicula sp,Cryptomonas sp, Chlamydomonas sp. and etc.The density and biomass of phytoplankton were both low for that the means for 48 reservoirs were 65.1×10⁴ ind./L and 0.503mg/L, respectively, and only three reservoirs had a standing crop larger than 1.00 mg/L. The gross and net primary production per unit of water column per day were 2.141 g O₂/L. d and 1.156 O₂/L.d, respectively. The lower primary production was in accordance with the lower standing crop.(2) Zooplankton42 genera and 77 species of protozoan were observed and had 11 dominant species such as Strobilidium gyrans, Strobilidium velix, Strombidium uiride and so on. 77 species of rotifers belonging to 33 genus were observed and Anuraeopsis fissa, Brachionus angularis, Brachionus angularis, Collotheca sp. Filinia maior were among the 15 dominant species. Cladoceran of 33 species in 14 genus were found, and Bosmina fatalis, Bosmina longirostris, Daphnia hyalina were among the 7 dominant species. 38 species in 24 genus of copepod were observed and had 6 dominant species such as Cyclops vicinus, Eucyclops serrulatus, Mesocyclops leuckarti and etc.The mean density and biomass of zooplankton for 48 reservoirs were 8036.8 ind./L and 2.015 mg/L, respectively. There were 9, 19, 11, 5 and 4 reservoirs whose biomass were lower than 1 mg/L, 1-2 mg/L, 2-3 mg/L, 3-4 mg/L and higher than 4 mg/1, respectively. (3) Benthic animals75 taxa of benthic animals were observed. The five dominant genera were Branichiura, Limnodrilus, Aulodrilus, Pelopia, and Cryptochironomus.The mean density and biomass of benthic animals in 48 reservoirs were 288.4 (43.2-928.2) ind./L and 8.760 (0.235-61.884) mg/L, respectively. The density of aquatic insects and oligochaetes were 83.7 ind./L and 178.6 ind./L, accounting for 61.9% and 28.8% of the total abundance, respectively. The biomass of mollusca, aquatic insects, and oligochaetes were 7.090 g/m2, 0.762g/m2, and 0.758 g/m2, accounting for 81.0%, 8.71% and 8.66% of the total, respectively.(4 ) Aqutic macrophytesAmong the 48 reservoirs, 20 reservoirs had aquatic plants distributed and 16 species of aquatic higher plants belonging to 13 genera in 12 families were observed. The dominant species were Vallisneria spiralis, Hydrilla varticillata, Potamogeton malaianus, Najas major, and Myriophyllum spicatu. Only 13 reservoirs had some extent of biomass and the mean density were 4.94 kg/m2.(5) Fishes59 fish species belonging to 52 genera and 16 families are observed, among which the cyprinid accounts for 37 species and 32 genera. The fish fauna is mainly the complex of Chinese rivers and plains3. Trophic classifications of reservoirsAmong 48 reservoirs, 5 were oligotrophic, accounting for 10.4%, 8 were meso-oligotrophic, accounting for 16.7%, 28 were mesotrophic, accounting for 58.3%, 4 were meso-eutrophic, accounting for 8.3%, and 3 were eutrophic, accounting for 6.3%. The oligotrophic reservoirs were all distributed by aquatic plants, while the eutrophic ones were mainly related to the inputs of domestic sewages and higher fishing intensities.4. Potential fishery yieldsAmong 48 reservoirs, 13 reservoirs had potential fishery yields of less than 15 kg/667 m2, accounting for 27.1%, 24 reservoirs had potential fishery yields of 15-30 kg/667 m2, accounting for 50%, 6 reservoirs had potential fishery yields of 30-50 kg/667 m2, accounting for 12.5%, and 4 reservoirs had potential fishery yields of more than 50 kg/667m2, accounting for 8.3%.5. strategies for rational exploitation of reservoir fisheriesThe main contents included: (1) strategies for macro-management; (2) fisheries development strategies for "reservoir cluster"; (3) strategies for optimizing main fisheries modes; (4) strategies for the protection of reservoir fisheries environments.