Food Relationship between Kura Goby (Ponticola cyrius) and Spirlin (Alburnoides eichwaldii) in the Tajan River, Mazandaran Province

This study, to study the food relationship between Kura goby and Spirlin because feeding both species from benthic invertebrate communities, were performed. Samples were caught on a monthly basis (from April 2012 to March 2013). In laboratory after primary biometry, gastrointestinal systems were removed and using binocular loupe, undigested food in the gut were identified and counted. Based on the results of the index relative length of gut, both species are carnivorous (P<0.05). Food preference index in both species be showed that order of Trichoptera was their main food. Investigation index of Ip with Costello method in Kura goby showed that order of Chironomidae in the spring season was dominant and proprietary prey. Survey this index in Spirlin showed that the Trichoptera in all seasons was public and dominant prey and other prey such as Ephemeroptera, Chironomidae, Simuliidae and crab (only in winter season) were public and rare prey. Food selectivity index (E) in Kura goby in all seasons for Trichoptera and Chironomidae (except spring season) was positive, as well as this index in spirlin in all season for Trichoptera was positive and showed that Spirlin tend to feed of Trichoptera at all seasons of the year. Index of feeding overlap index between showed that the least amount of overlap in the spring and highest of it was in the autumn. Considering to the results it can be stated that because the overlap of these two species in the ecological niche, there is food competition between them