| Qiandaohu Lake is the first large scale hydroelectric power station designed and builtby China in Zhejiang province ChunAnXian territory. It is Typical large deep lakes(reservoirs), lake fishing and eco-tourism are the two economic pillars of Qiandaohu Lake,silver carp and bighead carp aquaculture industry plays a vital role for the development ofChina’s freshwater fisheries. But there is an outbreak of cyanobacteria bloom between1998-1999for two consecutive years to raise awareness of a growing problem in the Lakeof the water pollution and eutrophication, Increased nutrients in water increased primaryproductivity of the water body and must be lead to fish feeding habits, communitystructure, and the food relationships change. At the same time, the invasion of exoticspecies and the upstream terrestrial input will be an impact on the structure and function of the food web. Qiandaohu Lake (reservoirs) is exogenous or endogenous lakes, the feedinghabits of silver carp and bighead carp, silver carp and bighead carp stocking for ThousandIsland Lake impact of invasive species Diet changes are there is an urgent need to addressthe problem.This paper uses the stomach content analysis method, PCR-DGGE fingerprintanalysis and stable isotope analysis combined study silver carp and bighead carp feedinghabits in Qiandaohu Lake,and the use of carbon and nitrogen stable isotope preliminarystudy the fish trophic level, relationships and food web structure,to provide some referencefor Qiandaohu Lake silver carp and bighead carp stocking, invasive species, terrestrialinput and eutrophication of the aquatic ecosystems. The main results are as follows:1. We get silver carp and bighead carp by monolayer gill net in the Qiandaohu Lake,take measurement and anatomy, and carry on the Microscopic analysis and DGGE analysison the Intestinal contents. The result shows: The grazing rate of silver carp (78.84%) ishigher than the grazing rate of bighead carp (63.78%). The Intestinal fullness of silver carphas the lowest level in summer (1.8%), and the Intestinal fullness of bighead carp has thelowest level in spring (0.7). The average value of Intestinal fullness of silver carp is higherthan bighead carp, It shows that the intensity of feeding of silver carp is higher thanbighead carp in the Qiandaohu Lake. From the analysis of the food composition, we findthat, The frequency of occurrence of zooplankton in silver carp and bighead carp is veryclose, it is different with the occurrence of phytoplankton: The frequency of occurrence ofCyanophyta in the food compositionis of silver carp is higher than bighead carp, thespecies of occurrence of Chlorophyta in the food compositionis of silver carp is more thanbighead carp, in general, the species of phytoplankton in the food compositionis of silvercarp is more than bighead carp. We has detected53different strips in the16S rRNA byDGGE fingerprinting, there are8-27strips in the intestinal contents of the differentindividuals (the average value is16.2. UPGMA clustering shows that there is significantoverlap between7silver carps and6bighead carps. We has detected45different strips inthe18S rRNA by DGGE fingerprinting, there are7-16strips in the intestinal contents ofthe different individuals (the average value is11.5). UPGMA clustering also shows thatthere is high similarity between7silver carps and6bighead carps. Except L1, he restrecord of7silver carps clustering together, when the all record of bighead carps clustering together. In conclusion, there is diet overlap on the feeding habits of silver carp in theQiandaohu Lake, and the intensity of feeding of silver carp is highter than bighead carp inthe Qiandaohu Lake.2. Both POM and carps in Qiandaohu Lake showed outstanding temporal variations inisotopic compositions. Moreover, positive correlation was found between δ13C of silvercarp and POM of δ13C and δ15N, suggesting that temporal variation of δ13C in POM waspreserved in planktivorous fish via food chain. The differences of δ13C among seston,zooplankton, and muscle tissue of silver carp and bighead carp ranged only0.37～3.88‰,indicating that plankton production was the primary food source of filter-feeding fishes,.indicating that plankton production was the primary food source of filter-feeding fishes.Using particulate organic matter As Qiandaohu Lake aquatic ecosystems stable isotopebaseline and by trophic level formula show that Silver carp, bighead carp trophic levels are2.43and2.66. According to the stable isotope mass balance model，we estimated that thecontributions of zooplankton to the diets of silver carp and bighead carp were43%and66%, the results showed that: zooplankton, silver carp and bighead carp both feedingphytoplankton carbon source, and the silver carp, bighead carp are phytoplankton andzooplankton for food.3. By using stable isotope techniques, this paper analyzed the organisms of foodsources and trophic level in autumn from September to November2011Qiandaohu Lake.Results show that δ13C values of each food sources span is large (29.7‰~23.9‰),among them the highest δ13C values of phytoplankton, the lowest δ13C values ofparticulate organic matter (POM). The food sources of δ15N value range is small, with thehighest phytoplankton (8.5‰), the lowest particulate organic matter the lowest (5.1‰). Incontrast to isotope value distribution trend of food sources,consumers of δ13C valuesrange is relatively small (29.7~21.6‰), and then δ15N range is relatively large (5.1‰~14.8‰). Consumers of trophic level from1.9to3.6, belong to the three nutrition levels,the trophic level of fishes all distribution between the third to the fourth trophic level, andinstead of feeding characteristics have good consistency, but as an invasive species ofherbivores fish Megalobrama amblycephala and omnivorous fish Ietalurus punetaustrophic level is as high as3.4and3.0, results show that the feeding habits of them havetaken place great changes in Qiandaohu Lake. Isotope tracer method research results also showed that the carbon source primarily is phytoplankton in Qiandaohu Lake waterecosystem. |
PDF Full Text Request