Bioaccumulation of heavy metals at cultured rainbow trout (Oncorhynchus mykiss) of Golestan Province, Iran

Rainbow trout is one of the most important breeding species in Iran and also in Golestan province. Monitoring and tracing of heavy metals is necessary to compare with existing standards, regarding the input of various pollutant sources, including heavy metals into water resources and eventually accumulation in aquatic organisms. This research project was carried out in winter to spring ۲۰۱۸ in rainbow trout farms of Golestan province in order to measure the lead and cadmium content of the samples. A total of ۳۰ metal samples were measured in water (۱۵ lead samples and ۱۵ cadmium samples) and ۵۰ metal samples (۲۵ lead samples and ۲۵ cadmium samples) in the fish of various sources of water supply (springs, rivers, wells, rivers and sea cages) in the east and west of the province. After drying and digestion of muscle samples in acidic solutions, the amount of lead and cadmium heavy metals was read using standard atomic absorption spectrometers in different lamps. A study on the mean amount of lead in different fields of salmon farming on the basis of water supply source showed that the amount of lead in the fish muscle of farmed farms with a source of water was much higher than other areas (۹۶۷ mg/l) and farms in the cage the lowest ۰.۰۱۳ mg/l. The average of total fish lead in the province was ۲۷۹ mg/kg, which is lower than the national and international standards. The amount of lead in the water supply sources of the studied farms was less than the virtual limit referred to in various sources. In the case of cadmium, the amounts in water and muscle were also negligible and were outside the detection range of the atomic absorption system, which indicates the health of water and fish in terms of cadmium. Comparison of heavy metal concentrations in Golestan province with other parts of the country showed that this amount was the lowest reported in the country, which indicates the health of Golestan province. Also, comparing the levels of Pb and Cd in salmon in the cages of Golestan province with similar values to other fish in the Golestan province showed that the number of trout heavy metals was much lower and had a better health. The levels of lead and cadmium in water and fish was lower than all national and international standards and were below the maximum authorized limit, so no risk to these end-users is noticed by the final consumer.

Keywords:

Aquatic , Pollution , Environmental Standards , Heavy metal , Bioaccumulation