Accumulation of arsenic during the growing period of rainbow trout (Oncorhynchus mykiss)

Rainbow trout (Oncorhynchus mykiss) was monitored for the duration of one year, from 2 to 14 months of age (n = 120). The study was performed on a farm with through-running water from the basin of water processing plant in the years 2007 and 2008. During the first months of fish life, we analyzed homogenized samples (n = 12) of rainbow trout bodies. From the 8(th) month the samples of twelve rainbow trouts were analysed. The total contents of arsenic and arsenobetaine were quantified in muscle, liver, spleen and bile separately. The total arsenic was determined by hydride technique AAS and arsenobetaine by high performance liquid chromatography combined with detection using atomic fluorescence spectrometry. The concentration of arsenic in homogenized body samples grew (P < 0.01) during the first months of life, from the 6(th) month of rearing no significant difference was found. The concentration of arsenobetaine in homogenized bodies was low during the first months and from the 6(th) month the concentration stayed on invariable level and amounted to 46 +/- 6% of total arsenic. The highest concentrations of arsenic and arsenobetaine in tissues ranked in the order muscle, liver, spleen and bile. In summer months the total arsenic in muscle was bonded in the form of arsenobetaine, in winter months the content of arsenobetaine dropped to 50% of total arsenic. The content of arsenic in liver samples remained the same during the entire monitoring, however, the ratio of arsenobetaine content altered. In summer months it reached the maximum 27%, in winter months it dropped to 7% of arsenic. The concentration of arsenic in spleen and bile decreased in winter months, arsenobetaine corresponded to the value assessed in liver. This study proved the effect of the small content of arsenic in feedstuff on accumulation of total arsenic and arsenobetaine in the tissue of rainbow trout during the growing period and season.