Feeding habits of Pelteobagrus nitidus in Dianshan Lake

The samples of stomach content of Pelteobagrus nitidus were collected at 6 stations in Dianshan Lake from August 2009 to July 2010,and the food composition was investigated based on the analysis of stomach contents.Results showed that P.nitidus preyed around the year and its feeding intensity had significant seasonal variations with the highest index of fullness in autumn and the lowest in summer and with the highest rate of empty stomach in spring and the relatively lower in the other seasons.Seven broad diet categories(11 small diet categories)were identified.Cluster analysis showed that the occurrance rate(F%),numerical percentage(N%)and percent index of relative importance(IRI%)were consistent in measuring contribution of each food category to P.nitidus.There were significant differences between weight percentage(W%)and each of the above three indices in measuring the contribution.The polychaete,benthic crustacea,aquatic insect and zooplankton were the main food sources for P.nitidus in terms of the above-mentioned four indices.The numerical and gravimetric compositions both significantly differed between seasons,the former also conspicuously differed among stations,but the latter did not display marked spatial variation with benthic crustacea as the predominant food source for P.nitidus caught at each station.There were obvious spatial changes in diversity of food compositon with the lowest in winter(0.15),and the largest H' at Station 5(1.52)and the smallest at Station 6(0.72).P.nitidus displays high plasticity in food composition by comparison with the feeding spectrum of this species from the other lakes.