The study of anthropogenic causes of the deterioration of the state of small rivers is the first step towards their conservation and restoration, improving the human environment as a whole. The aim of the study is the fishery and environmental assessment of water quality of small rivers in the Pripyat River basin (the area of right-bank tributaries in the middle part of the river) within the Rivne region in the northern-west region of Ukraine. The initial data for the assessment have been the

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... sults of monitoring (27 physical and chemical indicators) during 2010–2018. The assessment by the integral ecological index (Ie) has shown that the rivers belonged to the II quality class in terms of average values and were characterized as "clean" and "clean enough". According to the worst values, the rivers belonged to the II-III quality classes and were characterized as "fairly clean" – "slightly polluted" – "moderately polluted". The best water quality by the Ie index was established for the Zhabichi River within the urban-type settlement of Demydivka. Water quality of the Ustia River below the runoff of the cities of Rivne and Zdolbuniv has corresponded to IV-V classes i.e. was "dirty" and "very dirty" (high content of phosphates, nitrogen compounds, copper, manganese, and zinc). In terms of trophic state, the water of the rivers is mesotrophic (according to average values) and eutrophic (according to the worst values), except for the part of the Ustia River below the runoff of the city of Rivne, where the water is polytrophic. The rivers have failed to meet water quality standards for fishery water use by COD, BOD5, and heavy metals content (Cu, Mn, Fe, Zn).