A study on the some limnological characteristics and cage fish farming carrying capacity estimations of Sücüllü Dam Lake (Isparta, Turkey)

With this study carried out between May 2017 and April 2018 was aimed to determine the limnological characteristics, trophic status and to estimate the cage fish farming carrying capacity of Isparta Sücüllü Dam Lake (SDL). Sampling and measurements were made at 9 points, water and sediment samples were analyzed by titrimetric and spectrophotometric methods. Spatial and temporal variation of water quality parameters were determined by t-test and variance. And correlation analysis was applied for relationships between parameters. The average depth of SDL as 7.77 m, its length as 3000 m, its width as 275 m, the coastline as 6000 m and the coastline development (DL) as 1.86 were found. Across the study average the temperature 18.17 ± 2.49oC, pH 8.24 ± 0.04, EC 286.63 ± 10.34 µS/cm, DO 9.29 ± 0.44 mg/L, SSM 33,17 ± 10.41 mg/L, turbidity 13.25 ± 6.46 NTU, SDD 1.16 ± 0.09 m, Chl-a 1.85 ± 0.52 µg/L, BOD5 2.64 ± 0,87 mg/L, organic matter 5.67 ± 0.95 mg/L, total hardness 76.25 ± 4.09 mg/L CaCO3, alkalinity 82.25 ± 16.23 mg/L CaCO3, orthophosphate phosphorus 7,9±3,17 mg/m3 and total phosphorus 41,14±21,5 mg/m3 were determined. The parameters varied between stations and months. SDL's water shows eutrophic character in terms of TP and SDD according to the RSWQM trophic status index, and oligotrophic character in terms of Chl-a and DO. According to the Carslon index, while Chl-a TSI was oligotrophic, SDD, TP and mean TSI were determined at the eutrophic level. 6th station sediment TP value is higher than 7th station. Trout farming that applied around the point seems to have increased the TP concentration.In SDL 20 phytoplankton, 10 zooplankton taxa, 8 macroinvertebrate orders, 3 aquatic plants and 1 bird species were diagnosed. Fish species of Knipowitschia caucasica (B, 1916), Carassius gibelio (B, 1782), Cyprinus carpio (L., 1758), Oncorhynchus mykiss (W, 1792) were determined in the study. According to the Dillon-Rigler method, the rainbow trout carrying capacity of SDL was calculated as 0.4 ton/year at minimum water elevation and 18.94 ton/year at existing water elevation and 9.67 ton/year on average. It is concluded that it should be to take into account the area and volume data at the current and minimum water levels in the carrying capacity calculations in lakes with high water level fluctuation such as SDL and similar. It is seen that the fish production values recorded in the cages in SDL are higher than the determined carrying capacity. It is observed that SDL, which has a proportional small watershed and surface area, is under the influence of domestic wastes without treatment from settlements and agricultural activities that give nutrients to surface water. Wastewater treatment and good agricultural practices should be implemented to reduce the nutrient load of streams inflow SDL, and if cage fish farming is to be continued, production capacity should be reduced.