COMPARISON OF CRUSTACEA PLANKTONIC BETWEEN CULTURED AND NON-CULTURED LARGE RESERVOIRS

Lushui Reservoir, located at 113°53'21″E and 29°41'46″N, has a capacity of 7.06×109m3 with a surface area of 3.6×103 hm2 suitable for aquaculture. This reservoir had not been used for aquaculture. Catches from this reservoir were small in size and young in age. The silver carp and the bighead carp amounted to 1.48% in number and 13.4% in weight of the total catch. Fuqiaohe Reservoir, located at 110°52'30 ″E and 31°10'N, has a capacity of 5.4×109m3 with a surface area of 1.5×103 hm2 suitable for aquaculture. This reservoir had been used for aquaculture. The silver carp and the bighead carp amounted to 32.4% and 66.7% of the total catch in number, and 16.7% and 83.0% in weight in 1997. The planktonic crustaceans were sampled and analyzed from 11 sampling stations in January, April, July and October of 1991 in Lushui Reservoir, and from 14 sampling stations in April, July and October of 1997 and January of 1998 in Fuqiaohe Reservoir. The similarity indexes of the community structure of the planktonic crustaceans from each station were calculated with the equation of S=c/a.b. The similarity was classified with Fuzzy's cluster analysis method. The biodiversity of cladocerans in the two reservoirs were analyzed with the biodiversity indexes of Margalef d= (s-1)/lnN, Simpson D= 1/(∑(ni/N)2) and Shannon-Wiener H'=-∑(ni/N)×ln(ni/N). Results showed that, the dominant crustacean species in the two reservoirs were similar, mainly Daphnia hylina, Diaphanosoma brachyurum, Mesocyclops leuckarti etc. Calanoids dominated to some degree in the non-aquaculture reservoir, but not in the aquaculture reservoir. The body lengths of planktonic crustaceans in the two reservoirs were almost the same, but not of Leptodora kindti. The similarity index of planktonic crustaceans between the two reservoirs was 0.55.11 areas in the two reservoirs could be divided into 3 groups by the similarity of community structure of the planktonic crustaceans with the Euclidean Distance of cluster analysis. The indexes of Margalef, Simpson and Shannon-Wiener all decreased from the upper to the lower reaches. The 3 kinds of indexes in Lushui Reservoir were all higher than that in Fuqiaohe Reservoir. The densities and percentages of planktonic crustaceans from July and October in the aquaculture reservoir were both higher than that in the non-aquaculture reservoir. The differences of planktonic crustaceans in the two reservoirs were discussed from the view points of living environments and feeding of the silver carp and the bighead carp. Proper utilization of reservoirs for fisheries was strengthened.