| Taihu Lake is one of largest freshwater lakes in China, many large releasing worksin recent years have been launched to improve the water quality and the germplasmresource of fish in Taihu Lake. This paper focus primarily on the four major releasedfishes: H. molitrix, A. nobilis, C. alburnus, P. chinensis, employing field investigationand historical data, the main results as follows:1. The statistics results of historical number released and caught of H. molitrix, A.nobilis, C. alburnus, P. chinensis showed that: during2008to2011, the caught of thesefour released fishes increased significantly with the released number, and the releasednumber affect the population and structures of main fishes. The caught number of H.molitrix and A. nobilis had a positive correlation with C. ectenes and P. chinensis, butthe relationship is not significant （r=0.426, P>0.05; r=0.380, P>0.05）. The caughtnumber of C. alburnus had a significantly positive correlation with the caught numberof P. chinensis （r=0.673, P<0.05）, while the correlation between the caught numbers ofC. ectenes and C. alburnus was significantly negative （r=-0.560, P<0.05）. Therefore,the releasing of H. molitrix, A. nobilis, C. alburnus, P. chinensis has pronounced effectson optimization population and structure of the main fishes.2. The feeding habits of H. molitrix and A. nobilis in Taihu Lake were studied here,it shows that: In September, the percentages of the phytoplankton and zooplankton intotal fed quantity contained in the intestinal of H. molitrix and A. nobilis in Taihu Lakewere89.1%or70.6%and10.9%or29.4%, respectively, and the percentage ofcyanobacteria was74.5%or56%. The selective index of cyanobacteria for H. molitrixand A. nobilis was1.42or1.07, and that of cladocerans and rotifers were0.13or1.27and1.30or0.40, respectively. H. molitrix and A. nobilis feed chiefly on cyanobacteria in Taihu Lake. The analysis of the relationships between the caught number of H.molitrix and A. nobilis and physicochemical properties of the water in Taihu Lakedemonstrated that, the caught numbers of H. molitrix and A. nobilis had a negativecorrelation with TP and TN, however it not reached significant level （r=-0.4763, P>0.05;r=-0.3679, P>0.05）, indeed, it had a significantly negative correlation with Chl.a andCODMn（r=-0.7230, P<0.05; r=-0.6797, P<0.05）. So the releasing of H. molitrix and A.nobilis plays an active role in reducing the TP, TN, organic matter contents and thecyanobacteria biomass.3. From May to November in2012, the body length and body weight of the fourreleased fishes, H. molitrix, A. nobilis, C. alburnus, P. chinensis, were studied bysampling survey, the length and weight relationship of the four species wereW=1.5×10-5L3.0488（H. molitrix）; W=3.0×10-5L2.9244（A. nobilis）; W=2.0×10-5L2.8819（C.alburnus）; W=2.7×10-3L3.1175（P. chinensis）, and b value approximate to3, it indicatedthat the four species were uniform growth. The inflection point age of body weightrapid growth of the four species were4.03year old （H. molitrix）,4.29year old （A.nobilis）,5.06year old （C. alburnus）,10.7mouth old （P. chinensis）. The inflection pointage, body length, body weight of accelerated increment of the four species were:1.73year old,27.35cm,0.36kg （H. molitrix）;1.65year old,27.37cm,0.47kg （A. nobilis）;1.31year old,22.07cm,0.15kg （C. alburnus）;3.42month old,6.54cm,0.76g （P.chinensis）.4. A preliminary investigation of environmental condition of the germplasmresource protection area of Taihu Lake and its surrounding water areas had beenconducted from February to November in2012, the results showed: the water quality ofprotection area is better than that of surrounding water areas, which had reached thestandard of non-polluted or lightly-polluted levels, of which the diversity index andevenness index of phytoplankton and zooplankton were3.06or3.07and0.52or0.51respectively, furthermore, the water nutrition state index was29.56, was oligotrophic;and the concentration of TN and TP were0.486±0.017mg/L and0.021±0.001mg/L,respectively, the same as the second class of the national water quality standard;additionally, the waterweeds density was1058.28±20.6g/m2. These results might imply that the germplasm protection area of Taihu Lake give the promise of good waterquality and waterweeds condition for the growth and reproduction of C. alburnus and P.chinensis. |
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