عنوان مقاله [English]
Hilsa shad, Tenualosa ilisha, is an euryhaline, pelagic and anadromous species which is found in marine and freshwater water. It usually migrates more than 100 km to rivers in the breeding season. This survey, carried out from July 2006 to June 2007, included a total of 344 specimens all collected by gill net from the northern Persian Gulf, Bushehr coasts (Deylam waters). As studies show, Hilsa shad is a filterfeeder species and this study demonstrated that they fed on phytoplankton much more than zooplankton.The results indicate that the most abundant phytoplankton species belong to Bacillariophyta. In this phylum, genera Chaetoceros and Cocconeis had the most and the least abundance, respectively. After Bacillariophyta, there was phylum Pyrrophyta. In this phylum, genera Ceratium and Dinophysis had the most and the least abundance, respectively. On the other hand, the most abundant zooplankton species was related to phylum Arthropoda. Class of copepoda was approximately abundant in all months except August 2006 and May 2007. After Arthropoda, phylum Ciliophora with genus Parafavella was located as second food in feeding behaviour of Hilsa shad. Fluctuations between Arthropoda and Ciliophora were observed in comparison with other feeding groups. Abundance of other feeding groups was less than 5% of remainders in alimentary canal (stomach and intestine). The mean RLG was measured about 1/53 ± 0/22 (Range 0.88-2.34). The average (GSI) was measured about 0.752±0.448 (Range 0.04-2.64).