The effects of fish culture in floating cages on the seabed sediments and macrobenthos community in the southern Caspian Sea, Kelarabad

This study has been in order to investigate the effects of cage culture in the south of the Caspian Sea, Kelarabad. Sampling was in three direction of cages, East, West and South (the coast of Caspian Sea). For this purpose, four stations on each side of the cages was considered in terms of distance, the shadow (5 meters) to a distance of 1000 meters cages (control). Grain size analysis shows, the silt - clay (particles smaller than 63 microns) with mean (25/44- 98/4) and the average percentage of total organic matter (TOM) in deposits with mean (1/74-7/21). As the results show in all of the period of fine-grained particles was silt particles (mm ˂0/063), The highest the percentage of total organic matter at  station 3, and the highest percentage of organic matter showed in Station 3 (100 meter) to early (January), where it can because of sea currents (silicon and anti-silicon) from West to East. The results showed that the abundance of benthic invertebrate in station 4 (control) was higher than in the shadow of cages, which can be due to the cage culture and water flow. The lowest of the biomass was in the shadow of the cages and the highest was in station 3 (100 meters), in which can be due to presence of big species and high resistance to unstable conditions governing the location of marine cages to depend Cerastoderma lamarcki. According to the water flow that move and carry more organic matter from where the cages to this point has led to an increase in biomass. Shannon index range was determined between 0/29- 0/92 that reflects the diversity is low of the study area. Measurement of biological indicators such as diversity, abundance, indicator species, slight differences between the station bottom of cage and the station away from the cage, showed that some of these differences may be caused by fish farming in cages.