Mercury distribution in muscles and internal organs of the juvenile and adult Baltic cod (Gadus morrhua callarias Linnaeus, 1758)

Cod (Gadus marrhua L), a fish caught in the Baltic Sea, is very popular with consumers. Research on the distribution of mercury in cod tissues and organs was conducted on a group of adult (27) and juvenile (49) individuals in the years 2006–09. Total mercury concentration values in mature cod were always, on average, 1.7 times higher than those in juveniles. The highest HgT concentrations were found in the heart, while the lowest ones were found in the gills and gonads. The essential age-specific differences manifest in a relationship between the mercury concentration in fish muscles and brain. Mature individuals, i.e. of length >80 cm, accumulated Hg in muscles, most likely in an attempt to protect the nervous system from toxic exposure. In young individuals, more mercury was concentrated in the brain than in the muscles.. The distribution of HgT in organs as well as the low value of the [HgT]liver/[HgT]muscle ratio testify to relatively low-level mercury contamination in southern Baltic waters.