Investigating the effect of physcico-chemical and water trophy state on fish cage culture in the Aras Dam reservoir, West Azarbaijan

Factors such as increased global consumption of fish reduced marine fish harvesting, profitability and economics have increased the interest in fish culture in the cage. Fish culture needs a desirable water quality which is the best way to achieve optimum survival and growth. The purpose of this research is to investigate the water quality in terms of being suitable for fish cage culture in the Aras Dam Reservoir in West Azarbaijan. Sampling was carried out from 3 sites each with seasonal period from summer 2017 to spring 2018. Sampling was performed on the entrance, middle of the Lake and the crown of the dam from the water surface. Water temperature (º C), E.C. (µs/cm), T.D.S.(mg/L), was measured with WTW E.C.meter, pH with WTW pH meter, DO (mg/L) using oximeter WTW model 320. The TSI trophy index was calculated based on the parameters of total phosphorus and secshi-disc depth.  The transparency of water varied from 0.5 to 1.3 m between sampling sites. Generally, the TP at each sampling site was higher in summer than the other seasons. The trophic condition of the Aras dam is the hypertrophy which indicates the high phosphorus load and contamination from the agricultural runoff in the lake. The concept of carrying capacity, shortage of fresh water sources and the presence of hypertrophic conditions in all sites and seasons indicate that the ecological conditions of the Aras dam are not suitable for fish cage culture, and therefore is not recommended.