ESTIMATION OF WATER QUALITY ACCORDING TO THE EPT INDEX IN THE KAMCHATKA PENINSULA RIVERS IN AUTUMN, TAKING INTO ACCOUNT REGIONAL FEATURES OF THE FAUNA

The paper presents the results of the water quality assessing in the surveyed areas of the foothill Kamchatka Peninsula Rivers in the autumn of 2023. The EPT index of indicator groups of mayfl ies (Ephemeroptera), stonefl ies (Plecoptera), and caddisfl ies (Trichoptera) in the streams of the Bolshaya, Kamchatka, and Avacha River Basins varied within 8–16, which corresponds to the standard of good-fair or fair water quality. However, given that the fauna of these indicator orders of aquatic insects in the Kamchatka Rivers is slightly more than 20 % of that in the south of the Far East; these regional features are also refl ected in the indices when assessing water quality, in particular, in the number of EPT species. And if the water quality is considered good if there are 24–31 species in the rivers of the south of the Far East, then for the watercourses of Kamchatka such water quality, which we assessed with an index of 10 to 16, is quite justifi ed. It is also necessary to take into account seasonal changes in the fauna, since the samples were taken in September, when most of the indicator taxa left the streams, and a number of species of the new generation had not yet hatched. Our results can be confi rmed by studies conducted earlier in the areas of existing economic facilities on the Kamchatka Peninsula, which showed that the EPT index in the background river sections varied from 10 (Agi R.) to 13 (Tolmacheva R.), which is comparable with our results.