Feasibility study of cage fish farming based on physico-chemical parameters effective on water quality and eutrophication trend at less than 15 meter depth in southeast region of the Caspian Sea (Goharbaran region)

The aim of this project was to study the feasibility of cage fish farming based on the evaluation of physico-chemical parameters effective on water quality and the trophic status (scaled and unscaled) at various depths of water and different months in the southeast of the Caspian Sea (Goharbaran region). The total numbers of 154 samples were collected at eight stations from three depths (5, 10 and 15 m) during 12 months. Results showed that the amounts of water temperature, transparency, pH, dissolved oxygen, BOD5, total alkalinity and TSS ranged from 9.00 to 29.00˚C, 0.50 to 12.00 m, 8.05 to 8.74, 5.76 to 12.85, 21 to 195 and 0.00 to 0.12 mg/l, respectively. In addition, the values of NH4, NH3, NO2-, NO3- and PO4-3 ranged from 0.007 to 0.051, 0.001 to 0.010, 0.002 to 0.015, 0.043 to 0.477 and 0.014 to 0.077 mg/l, respectively. Scaled and unscaled trophic index were 3.42-5.52 and 2.61-5.85, respectively. Therefore, the proper temperatures for cultivation of salmonids species in this area were begun in October and ended in March. In the current study, results of pH and dissolved oxygen were consistent with the standard range of pH (7.80-8.50) and dissolved oxygen (>5 mg/l) for cage fish farming. Although, Goharbaran region were appropriate for cage fish farming in terms of nutrients, but this region was evaluated as mesotrophic (5.97±0.73) with high risk of eutrophication (>4).