Studies On Feeding Ecology Of Anchovy In Yellow Sea

Anchovy (Engrauli japanicus) is an important link in the ecosystem of Chinese Yellow Sea and East Sea. In order to determine its importance in trophic relationships, it is necessary to quantitatively estimate the characteristics of feeding ecology. In this study the feeding rhythm, daily ration and feeding pressure of anchovy were investigated, the main research results were as follows:(1) The gastric evacuation rate of anchovy in different growth periodThe gastric evacuation rate of anchovy in different growth period was determined in the simulated field conditions and laboratory conditions. Goodness of fit of three mathematical models in common uses for the gastric evacuation, including linear, exponential and square root model, was compared. According to the statistical test, the three models could all fit quite well the gastric evacuation of anchovy in different growth period, the further assessment indicated that the exponential model was best suitable for quantitatively describing the fish's gastric evacuation, square root model came second, linear model was worst.(2) Daily ration of anchovy in the simulated field conditionsIn the simulated field conditions Daily rations of anchovy were 10.184±3.135 g·100g^-1d^-1 and 12.354±0.604g·100g^-1d^-1 in feeding period (Sep) and feeding period( Oct ) respectively.(3) Feeding rhythm and daily ration of anchovy in natureBased on the analysis of stomach contents of sampled in the survey of Yellow Sea carried out from January 2002 to September 2009, The feeding intensity showed obviously diel variation in each voyage, the peak appeared from 6:00 to 10:00 and from 14:00 to 16:00, the feeding intensity is higher in the daytime than at night. The daily ration of wintering anchovy showed significantly annual variation from 2002 to 2005, the max value was 1.0550g·100g^-1·d^-1 in 2005, the min value was 0.208g·100g^-1·d^-1 in 2002. The daily ration appeared obvious variation in different growth periods, the max value appeared in the spawning period, the feeding period second, the mix value was in the over-winter period.(4) The comparison of daily ration of anchovy measured with two methodThe daily ration of anchovy in feeding period in the simulated field conditions was 4 times of that in nature.(5) Feeding pressure on zooplankton of anchovyThere was a consistent seasonal variation between feeding pressure on standing stocks and on production of zooplankton of anchovy. The value of feeding pressure on standing stocks and production of zooplankton of anchovy were 0.971 and 3.179 in spring; 0.252 and 2.508 in autumn; 0.017 and 0.526 in winter respectively.