SELECTED HEAVY-METALS IN THE TISSUES OF FISH IN THE LUZNICE RIVER

Water quality in the upper course of the Luznice river is affected by the high-lead waste waters drained into the river from the glass works. Fish of different age were sampled from the Luznice and its tributary, the Kostenicky brook, directly affected by the waste waters, and were subjected to analysis. Roach (Rutilus rutilus) from Kostenicky brook had in its kidneys 0.67 mg of lead per 1 kg of fresh matter whereas the roach caught in the Luznice had ten times less lead in their kidneys. Lead contents in muscle did not change with age but the levels in the liver and kidney declined. Cadmium content in the kidney and liver of the roach declined until an age of seven years. In the bream (Abramis brama) older than ten years the cadmium levels increased with age. The content of lead increased only in the older specimens. Zinc content in the tissues of the fish declined with increasing age, except in the kidneys of pike (Esox lucius) in which it showed a slight increase. Older fish also had less manganese in their tissue than recorded in the younger specimens. The levels of the studied metals in fish muscle never exceeded the admissible values; only the kidneys of the pike and roach did contain more zinc than the hygienic limit of 80 mg per kg.