Changes in mercury concentration in muscles, ovaries and eggs of European eel during maturation under controlled conditions

Abstract

The degradation of the environment, namely due to pollution causes increasing impact on the organisms living on it, especially those at the top of the trophic chain. The accumulation of heavy metals such as mercury in live organisms may have a negative effect on the efficiency of reproduction. The aim of this study was to determine the mercury (Hg) content in muscles, ovaries and eggs during final maturation of gametes and after ovulation of European eel females. To this end, 65 (53 as treated and 12 as control) female European eels collected in Poland were analysed for mercury content. Eels were caught during commercial fishing activities in fresh water in the Warmia and Mazury region. Females were stimulated with carp pituitary homogenate (CPH) at 18mgkg−1, at 5-day intervals, for 20 weeks. The hormones were not given to the fish in the control group. The mercury content in tissues was determined by atomic absorption using a Milestone DMA-80 and analysis showed statistically significant differences (P < 0.05) between the content of mercury in muscle, ovary and eggs. The total mercury concentration in females following spawning increased in muscles and ovaries. Female eel eggs (0.0031 ± 0.0003mgkg−1 w/w) were found to contain eight times less mercury than their ovaries (0.026 ± 0.002mgkg−1 w/w) and 78 times less than their muscles (0.24 ± 0.03mgkg−1 w/w). The concentration of mercury in both muscles and ovaries in fish increases after spawning, which can additionally confirm that mercury is transmitted in small amounts from the mother's body to eggs.