Importance of gammarid ( Pontogammarus maeoticus) in larval bony fish diet at the coast of Khazarabad in Sari at southern Caspian Sea

The aim of this study was to determine the importance of gammarid (Pontogammarus maeoticus) in the diet of larval bony fishes, in the Caspian Sea. Sampling of coastal gammarus and larvae was conducted in two phases (December 1389 and April 1390), from 12 stations (in four districts, each with 3 stations) in this study. Fish were caught at 0.5 to 1 meter depth, using a mesh cloth (the aperture diameter of one millimeter) of 0.5 × 1 meter dimension and were immediately fixed with 70 % alcohol and transported to the laboratory. Gammarus were caught from the coast sand using a handmade rectangular fishing net of one mm diameter aperture and 40×60 cm dimension. In the winter of 1389, 98 fish and in the spring of 1390, 107 species of fish were sampled. The sampled specimens included Liza saliens, Rutilus frisi kutum, Atherina boyeri, Benthophilus ctenolepidus, Gasterosteus aculeatus with the weight range of 0.45 – 3.25, 0.6 – 3.27, 0.81 - 5.88, 1.17 – 3.67 and 1.27 – 1.96 gram, respectively. In order to identify the fish species which are consumers of gamarids, gastro intestinal contents were analysed. The results showed that species collected have different amounts of coastal gammarus nourishment. In winter the highest amount with an average of 8.25 percent in 1389, related to Rutilus frisii kutum and in the spring of 1390 with an average of 1.92 percent related to Liza saliens.