Effect of Low Doses of Mercury on the Temperature Tolerance of Juvenile Carp Cyprinus carpio

Abstract Data on the effect of mercury supplied with food on the temperature tolerance of juvenile carp Cyprinus carpio L. were obtained for the first time in a long-term experiment. The total mercury content in the fish feeds of two experimental groups was 0.02 mg/kg and 0.27 mg/kg of crude weight. After 5 months of the experiment, the mercury content in the muscles of the fish that received a higher concentration of mercury increased 26 times, and those with a lower concentration, 5 times. The temperature tolerance of juvenile carp was determined monthly using the methods of critical thermal maximum (CTM) and chronic lethal maximum (CLM). The accumulated mercury in muscles up to 1.82 mg/kg did not have any significant ( p > 0.05) effect on the studied temperature characteristics of carp both under conditions of rapid (∼8°C/h) and slow (1°C/24 h) water heating. The average CTM values were 35.8–36.1°C, those of CLM were 39.6–39.7°C in fish of all experimental groups. At the same time, slow heating (CLM method) contributed to an accelerated accumulation of mercury in the muscles of fish receiving both low and higher doses of mercury. Apparently, the level of accumulated mercury did not cause any significant failures in the operation of systems that ensure temperature tolerance of the body; however, higher background temperatures significantly accelerated its accumulation.