| This study consists of two parts. The first part is that according to research strategy- simplified version of food web, by analyzing stomach samples of important resources species collected during two synoptic surveys of the Yellow Sea and the East China Sea in 2000 and 2001, and combining with historical studies in the Bohai Sea and Yellow Sea, feeding competition, trophic level and food web of high trophic levels in China coastal seas are discussed. The main results are as follow:1. By analyzing stomach samples, the main food composition and feeding competition of the major fish in the Yellow Sea and East China Sea were studied. The results indicated that the main competition food was Euphausia pacifica, Crangon affinis and Engraulis japonicus in the Yellow Sea and Euphausia pacifica, cardinal fish, skinnycheek lantemfis, firefly-fish, largehead hairtail and anchovy in the East China Sea. The major fish used feeding different prey species, different size of prey and feeding time and microhabitat partitioning to reduce feeding competition and maintain the dynamic balance of community structure. The change of fish assemblage can influence the feeding competition between fish. On the other hand, the feeding competition also can affect the change of fish assemblage.2. The mean trophic level of high trophic levels in each seas declined all about 0.2 · decade-1, higher than global trend. The fluctuation in trophic level of high trophic levels was caused mainly by the change in community species composition and the interannual variation in single species trophic level, and the latter was related directly to colonial individuals getting smaller and food trophic level getting lower. The changes in trophic level of high trophic levels are important indicator for understanding thebioproduction dynamics in marine ecosystem, therefore, it is suggested that the international standard shall be used to divide and calculate trophic level, and the long-term and systematic monitoring on these changes are needed.3. Food web structure of high trophic levels in the East China Sea is morecomplex than the Yellow Sea, and there are area differences of food web in two seas: (1)In the Yellow Sea, whether at autumn or at spring, food web structure of the inshoreshallow waters are more complex than the cold waters, and food web structure of thecold waters at autumn is the simplest; food web structure of the inshore shallow watersat autumn is more complex than at spring. (2) In the East China Sea, although mere aremany differences in species composition between the inshore and the offshore waters atautumn, food web structure is similar. At spring, food web structure of the inshorewaters is the simplest, and food web structure of the ofishore waters is the mostcomplex. Comparing food web structure of the Yellow Sea in 2000-01 with in 1985-86,the number of important species decreasing, composition simplifying and trophic leveldeclining all result in simplifying food web structure. Food web of the Bohai Sea amonglast 40 years also has the same changes.The second part is preliminary studies on marine fish trophodynamics. Feeding, ecological conversion efficiency and energy budget of red sea bream (Pagrosomus major) and Sebastodes Juscencens are researched by using bioenergetic methods. Gastric evacuation rate and effect factors of red sea bream, black sea bream (Sparus macrocephalus) and Sebastodes Juscencens are analyzed by stomach sampling continuously. At the same time, biochemical and energetic composition of more than 100 important species in China coastal seas are determined. The mam results are as follow:1. The optimal appetite temperature is 18,76^, at which Sebastodes Juscencens may have the maximum consumption ration of 356.80 J/g.d. The relationship between the maximum ration level and body weights and temperatures is: Rm^ e (-7 161.63+1 045.25T - 27,86T2)W"0-3932. The energy budget model can be write as: 100,4 ? 30.37/? +69.63G and 100A = 48.89i? + 51.13G, respectively at 5kg m"3 ft 8kg m'3. This suggests that the energy in the food consumption of low-density group is allocated more to growth than high-density group.2. The compensatory growth in red sea bream which is deprived food for short time results from significant increase of the feeding rate in the recovery growth; but the compensatory growth which is deprived food for prolonged time results from significant increase of the ecological conversion efficiency in the recovery growth. The mechanism of ecological conversion efficiency in recovery growth after starvation is due to: 1) high feeding rates low consumption; 2) secretion and activity of digestive enzyme increasing. The recovery growth of Sebastodes fuscencens is different with weight: the low weight group significantly increases feeding rate to obtain compensatory growth; but the high weight group significantly increases ecological conversion efficiency to obtain compensatory growth.3. For gastric evacuation rate of red sea bream, when remain food in stomach is expressed as wet weight, exponential model is the best; as dry weight, square root model is the best. It is exponential correlation with temperature: r=0.0186e01075:r. For gastric evacuation rate of black sea bream, whether remain food in stomach is expressed as wet weight or dry weight, linear model all are'the best. For Sebastodes fuscescens, weight has the significant effect on the gastric evacuation rate, but there is no clear tendency; It is exponential correlation with temperature: r=1.53e0086r; effect of food species on gastric evacuation rate is more important than food energy content.
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