Status Quo Of Fisheries Ecological Environment In The Section Of The Yangtze River From Yichang To Chenglingji And The Strategies For Their Protection

In order to know well the background status of fisheries ecological environments in the section of the Yangtze River from Yichang to Chenglingji before the construction of the Three Gorges Project, and to objectively analyze and evaluate the effects that the Project might bring along, the author investigated in successively several years (1997-2002)before the construction the status quo of 18 physico-chemical indices of the water ( water temperature, pH, suspended solids, permanganate index, ammonia nitrogen, unionized ammonia, total phosphorus, copper, zinc, lead, cadmium, mercury, oil, volatile phenol, cyanides, hexavalent chromium and arsenic) planktons and 5 indices of residual poisons (copper, zinc, lead, cadmium and volatile phenol) in fishes in the spawning grounds of Chinese sturgeon and those of the four major Chinese carps,which distributed in the Yizhi section and in the Jingjiang section respectively, by combining physico-chemical monitoring method with biological monitoring method. And their background values were put forward by applying statistic methods at the first time. Also, according to the water quality standards for fisheries, the environmental quality standards for surface water and hygienic standards in foods, etc, a large number of data obtained were evaluated by the standard index evaluating method, the comprehensive assessment method of river water quality, Saprobic System method, and comprehensive assessment methods of residual pollutants in fishes, etc, respectively. Besides, strategies for fisheries ecological environments protection by alleviating unfavorable effects were brought forward. And the main results were as follows:1 , In the spawning grounds of the Chinese sturgeon,which distributed in the Yizhi section, The data on water temperature, pH, suspended solids, permanganate index and total phosphorus were subordinated to normal distribution. While that of unionized ammonia, copper and zinc conformed to log-normal distribution And their background values (the 90 % of the regression coefficient's confidence interval ) were 18.6 (18.5-18.7)°C for water temperature, 8.02(7.97-8.07) for pH, 223.2(189.8-256.6) mg/L for suspended solids, 1.6(1.56-1.64)mg/L for permanganate index, 0.016(0.010-0.025)mg/L for unionized ammonia, 0.075(0.067-0.083)mg/L for total phosphorus, 0.047(0.040-0.054)mg/L for oil, 0.012(0.010-0.014)mg/L for copper, 0.042(0.037-0.047)mg/L for zinc, respectively. The concentrations of lead, cadmium, mercury, volatile phenol, cyanides, hexavalent chromium and arsenic were below the minimum detection limits by the corresponding analysis methods or their detection rates were very low. So the relevant minimum detection limits were fixed on their background values.2,Evaluated by the standard index evaluating method, the 18 physico-chemical indices of the water mentioned above were up to the water quality standards for fisheries except oil. It was higher than the content of the standard at few stations in Yizhi section. And judging by the comprehensive assessment method, the water quality on the whole conformed to environmental quality criterion of grade II for surface water, and could meet the demands for the reproduction of Chinese sturgeon.