The diet of big-scale sand smelt Atherina boyeri caspia (Risso, 1810) in the southeastern coast of the Caspian Sea

Big-scale sand smelt is one of the fishes with high ecological value, which consume by fishes such as sturgeon in the Caspian Sea. In this study, 191 samples of Big-scale sand smelt from southeast coast of the Caspian Sea were collected seasonally from December 2013 to September 2014. In the present study, food items and the relative index of gastrointestinal (RLG), stomach emptiness index (VI) and feeding intensity (IF) were determined. The fork length, weight and age (mean ±SD) were 7.70 ± 1.09 cm, 3.64 ± 1.49 g and 2.00 ± 0.81 year, respectively. This fish with a relative gastrointestinal tract length of 0.46 ± 0.06 (mean ± Standard Deviation) can be considered as a carnivorous fish. The average of empty stomach was 45% showing big-scale sand smelt is a relatively voracious feeder. The average intensity of feeding (mean± Standard Deviation) 535±221.21, as a moderate level for this fish in the region. Gammarus (benthos) and Daphnia (zooplankton) were the favored food for this fish. This study also showed opportunistic hunting activities of this fish.