MACROZOOBENTHOS OF MOUNTAIN RIVERS OF THE TRANSCARPATHIAN REGION AS A FORAGE BASE OF BENTHOPHAGOUS FISHES AND SAPROBITY INDICATOR

Purpose. To study qualitative and qualitative indices of macrozoobenthos as one of main components of the forage base of benthophagous fishes in mountain river reaches of the Transcarpathian region and determination of their saprobity level. Methodology. Thhj,9.e study was carried out in summer period of 2009 in mountain river reaches of the Tisa river catchment. Zoobenthos samples were collected by a Surber sampler (25 × 25 cm) on the bottoms of different fractions with different water flow rate (riffle, run, pool). Collection, processing and interpretation of the obtained data was carried out according to generally accepted hydrobiological methods developed for mountain river studies. Saprobity was of the studied rivers was calculated by Pantle-Buck formula. The Zelinka-Marvan saprobity index was used for calculations. Findings. Qualitative and quantitative macrozoobenthos indices have been studied. The number of zoobenthos on the investigated river sections ranged from 416 to 7712 ind./m2 with biomasses from 2.96 to 83.84 g/m2. The major portion of the zoobenthic biomass in the majority of rivers was due to caddis fly larvae composing up to 93% of the total biomass. An important role in the total biomass of the zoobenthos also belonged to mayfly (up to 53%) and stonefly (up to 55%) larvae and in lower degree amphipods (up to 39%), chironomid larvae (up to 14%) and aquatic coleopterans (up to 5%). According to the calculated potential fish productivity, the mountain rivers can be apparently separated into three groups: little productive (4.2–12.7 kg/ha), medium productive (13.2–21.6 kg/ha) and high productive (25.3–85.3 kg/ha). Mountain river reaches of the Transcarpathian region were found to belong to pure χ-saprobic, and о- і β-mesosaprobic zones, the saprobity index in which ranged from 0.35 (Rika river) to 1.7 (Shipot river). Originality. For further calculation and assessment of brown trout (Salmo trutta) and European grayling (Thymallus thymallus) stocking amounts for mountain reaches of the Tisa River basin, we investigated qualitative and quantitative indices of macrozoobenthos as one of major components of the forage base for benthophagous fishes and calculated their potential fish productivity. Practical value. Data on macrozoobenthos biomass and saprobity of mountain river reaches can be used for calculation and assessment of the possibility of stocking the studied river with juvenile brown trout and European grayling as well as for calculation of possible damages resulting from construction of small HPP (a tendency for construction of which on the Transcarpathian rivers lately becomes more significant)