Water Quality Status Of YangCheng Lake And Initial Study On Ecological Crab Culture

Eriocheir sinensis H. Milne-Eswards, known as river crab, is a special product in China, which belongs to Crustacea, Decapoda, Grapsidae, Eriocheir. It is one of aquatic products in rising demand at home and abroad market in recent years. Crab has been an important aquaculture object in China for its rapid growth speed, high survival rate, convenient transportation, rich nutrition and special taste. However, as the current rapid economic and social development, the lake ecological environment is facing unprecedented pressure. The improvement of people's living standards makes the demand of pollution-free crab grow rapidly day by day. So, crab ecological aquaculture industry is facing with a considerably difficult challenge.In this study, we monitored and evaluated the water quality of YangCheng Lake from 2005 to 2007, and preliminary researched the impact of crab barier net aquaculture for pollution load, we also summarized barier net aquaculture technique of YangCheng Lake crab simultaneously. This study will provide some reference for the further development of YangCheng Lake crab industry. The main results are listed below:1 The actual condition and appraisal of water quality of YangCheng LakeWe monitored the water temperature(WT), diaphaneity(SD), pH, dissolved oxygen(DO), total nitrogen(TN), total phosphorus(TP), permanganate salt index(CODMn), fluorid and heavy metal of water samples from 7 sampling points which were distributed in YangCheng Lake from 2005 to 2007. We evaluated the actual condition of water quality of YangCheng Lake by ways of water pollution index according to theâ…¢grade water standard of NY5051-2001 & GB3838-2002. The results revealed that the serious pollutant was TN, secondary pollutant were TP and COD, medium was fluorid, then pH and DO. In 2005 to 2007, the principal pollutant of YangCheng Lake was TN for sharing the largest pollution load index and the secondary were TP and COD. The lowest nitrogen content of water was 2.20mg/L which had exceeded theâ…¤grade water standard. The highest phosphorus content was 2.14mg/L that had also exceeded the V grade water standard. In a word, YangCheng Lake was in a eutrophication.2 The preliminary study on pollution load of crab barier net aquaculture in YangCheng LakeWe investigated and counted the crab aquaculture mode of past years of local owners. And we calculated the total quantity of N and P which were discharged into YangCheng Lake by ways of material balance. The results showed that the import of N and P of lhm2 crab barier net were 63071.5g and11956.56g; the export of lhm2 were 46995g and 5748.75g. In total, the emissions of N and P of lhm2 barier net were 16.08kg and 6.21kg. The emissions of N and P of one year in YangCheng Lake were 86.4t and 33.4t.3 The initial study on culturing density of barier net ecological aquaculture of crab in YangCheng LakeA result after the crabs culturing density experiment showed that the suitable culturing density was 300 crabs per 667 hm2. The survival rate, yield and recapture rate could reach to the best in such a density. At the same time, the water quality happened apparent change.