Comparative study of the impacts of fish cage culture on some environmental factors and Macrobenthic communities in offshore farms in the southern Caspian Sea

Abstract

The aim of this study was to investigate the effects of fish cage culture on Macrobenthic in the southern Caspian Sea. Samples were collected in two offshore farms with four floating polyethylene cages with a production of 60 tons for 5 months in 2015. Sampling was performed of macrobenthos, physicochemical, and sediment in January, March, May, and August at the depths of shade, 50, 100, and 1000 m in three geographical directions (east, west, and south) of the farm. Macrobenthic analysis showed Hypaniola kowalewskii and Streblospio gynobranchiata were predominant, which resulted in an unusual condition due to the effectiveness of the marine farm. There was a linear relationship between environmental factors and macrobenthos communities under the RDA analysis test and the water temperature was the most crucial factor in the density of the dominant species in both fish farm sites. The dominant Macrobenthic species were subjected to environmental conditions in addition to the influence of temperature, salinity, pH, dissolved oxygen, nitrogen, and phosphorus compounds. This situation can be attributed to the hydrological conditions of the studied area; low production of fish, a short period of fish farming, suitable depth of cages established and different water flow directions.