Mercury content in the organs fish from different reservoirs of the Ustyuzhensky District of the Vologda Region

This article examines the levels of accumulation and distribution of mercury in the tissues of fish of different trophic status from different reservoirs (the Mologa River, the Chagodoscha River and Lake Vanya), located in the western part of the Vologda Region, is characterized by favorable natural and climatic conditions for methylation processes. Mercury content was determined in 108 tissue samples from 87 individuals of four fish species –Rutilus rutilus(Linnaeus, 1758);Abramis ballerus(Linnaeus, 1758);Perca fluviatilisLinnaeus, 1758;Esox lucius Linnaeus, 1758. The total mercury concentration was measured on a mercury analyzer RA-915M with a PYRO+ device (the lower limit of mercury detection in samples is 0,001 mg/kg). The mercury index values in the tissues of the studied fish species range from 0,02 to 1,7 mg/kg, crude weight. The minimum average values were noted for a predominantly non–predatory species, roach (0,12 mg/kg, crude weight), the maximum average values were noted for a typical predator, common pike (0,64 mg/kg, crude weight) (in some individuals it exceeded 1,5 micrograms/g). Intermediate values are typical for perch and tuna (on average 0,33 mg/kg and 0,37 of the crude weight, respectively). It was found that in 28% of the studied individuals, the mercury content exceeds the regulatory levels in force in the Russian Federation (0,3 micrograms/g for non-predatory species and 0,6 micrograms/g for predatory fish species).