Effect of the selected physico-chemical parameters on growth of rainbow trout (Oncorhynchus mykiss) in raceway system in Iran

A study was conducted to evaluate the correlation between selected physico-chemical parameters of water and their effects on growth of Rainbow trout (Oncorhynchus mykiss) in raceway system in the area of Sarab Gerdu, Iran. The samples were collected from twenty raceways (270- day old fish, surface area 55m2; flow rate 150 ls-1; total production 15 T). Physico-chemical parameters were the fluctuations of total ammonia nitrogen, dissolved oxygen, turbidity, nitrogen (nitrates), phosphorous (phosphates), total dissolved solids, electrical conductivity, fluoride, boron, pH, temperature, total hardness, and alkalinity. Multivariate analyses were conducted employing three categories of parameters including A, B and C. The results of the study showed that temperature and pH variations were similar. Dissolved oxygen with negative similarity coefficient, _0.618 was located in the third category while positive coefficient, 0.479 of other parameters except for pH and temperature (second category) and dissolved oxygen (third category) was located in the first one. pH value was not in a standard range due to increase in water temperature. This, in turn had impact on other parameters, such as unionized ammonia, a toxic chemical, to fish. Our result demonstrated that nitrate concentration is the most significant chemical parameter for fish growth in this area. Similarity, increase in concentration of dissolved oxygen in the water (from 3.30 mgl-1 up to 12 mgl-1) was necessary to promote productivity.