Feeding investigations of silver carp (Hypophthalmichthys molitrix) fingerlings with emphasis on dominant phytoplanktons

Abstract

In order to study phytopague fingerlings feeding in fish ponds, simultaneously to the beginning of warm season and cultivation, fingerlings of 3-5 gr from 4 ponds in Mazandaran province were captured, fixed with formalin, then transferred to the plankton determination laboratory of Caspian sea ecologic institute. Based on carried out studies on the first and the end party of their intestine and the pond water, phytophague fingerlings feeds on phytoplankton, zooplankton and detritus. But the essential nutrition was on phytoplankton and detritus. Planktonic groups were formed of Cyanophyta, Chlorophyta, Chrysophyta and Euglenophyta. But in addition to these four groups Pyrophyta was present in fish pond water. Relative abundance of these nutrient organisms in water and intestine was different. Also in most cases a direct relation was observed between the intensity of water organisms and intestine ingredients. Based on this study, essential differences of digestion were observed following to the source of nutrition and the most difference were considered in digestion of Chrysophytes, Cyanophyta and Chlorophyta. Base on the results of this study we propose to make more studies on fertilization and the proportion of different fertilizers in fish ponds in order to obtain easily digestible phytoplankton thus increase in fish exploitation.