Determination of the biodiversity indicators under cage culture of rainbow trout conditions in the Abbas Abad area, southern basin of the Caspian Sea

This study was designed to determine the probable effect of rainbow trout cage culture on the biodiversity indicators in the Abbas Abad area, southern basin of the Caspian Sea. For this purpose, biological samples (benthic macro invertebrates, phytoplankton and zooplankton) were collected at distance of 5, 50, 100 and 1000 m from the cages in December 2014 (before the culture period), March and April (production period) and August 2015 (after the culture period). In this study, 9 taxa of benthic macro invertebrates (with the dominance of polychaetes; Streblospio gynobranchiata and Hypaniola kowalewskii) and 42 species of phytoplankton belonging to five phyla (with the dominance of Bacillariophyta) were identified. A total of 10 taxa of zooplanktons were identified with the copepod; Acartia tonsa being the dominant taxa as well. The results showed that the distribution and abundance of biological community were significantly affected by the seasons (p < 0.05) where as it was not affected by the distance from the cages (P>0.05) and in most cases, changes of biodiversity indicators were not affected by cage culture activity. It seems that the rainbow trout cage culture in the Abbas Abad region no remarkable effect on the biodiversity indicators in the vicinity of small scale fish cages due to short duration of cage culture and strong water currents, so that observed changes were more associated with seasonal fluctuant.