The Fauna of the River Dovey, West Wales

Abstract

This river is 30 miles long, has a large watershed, heavy rainfall, and high floods. The river water is soft, somewhat acid, well oxygenated, normally clear, and virtually unpolluted. All parts of the stream support an abundant algal and bryophyte flora, but the scanty phanerogamic vegetation is confined to the lower part of the stream. The fauna was sampled in a partially quantitative manner at 4 stations over 6 months. 132 spp., mostly Arthropoda, were found. The fauna became progressively richer toward the mouth of the stream and changed from lotic in the upper and middle portions to predominantly lentic. Mollusca were scarce, probably duo to the acidity and low Ca content, but there were good numbers of fish present. The study was undertaken for comparison with the Ystwyth river which is zinc polluted. The Ystwyth river contained only 58 spp., all but 10% of which occurred in the Dovey river. The poverty of the Ystyth river is partly due to the toxicity of the Zn salts, and in addition to its being heavily silted, shallow, swift flowing, and devoid of vegetation.