Sieve methods

Preface: The main goal of this work is to give an introductory account of sieve methods that would be understandable with only a slight knowledge of analytic number theory. These notes are based to a large extent on lectures on sieve methods given by Professor Van Lint and the author in a number theory seminar during the 1970-71 academic year, but rather extensive changes have been made in both the content and the presentation...

The communities of running water in Cumbria

For conservations of nature to be effective. there must be an understanding of what is present to be conserved. Thus in order to conserve the communites of the Cumbrian rivers, there must first be surveys to determine the spp present and their relative numbers. This has been carried out for many years, by a number of workers. It has been shown that the communities present are influenced by the substratum, the flow, the chemicals present, water temp and predation. Findings of the work on the River Lune were given at a seminar on the rivers of north-west Europe, held at Amiens in November, 1975. The proceedings of the seminar are to appear in special numbers of Bulletin francais de Pisciculure.

Joint Anglo-Soviet biological surveillance exercise on River Dnieper

As one part of an on-going programme concerned with environmental protection as provided for under the terms of a UK/USSR Joint Environmental Protection Agreement signed in London, 21 May 1974, a seminar — ”The elaboration of the scientific basis for monitoring the quality of surface water by hydrobiological indices” was held at Valdai in Russia 12—14 July, 1976. As a continuation of this theme it was agreed that delegations of hydrobiologists from each side should carry out reciprocal visits to carry out comparative field tests on selected systems of biological surveillance in use in the respective countries. In May 1978 a team of British hydrobiologists visited the USSR, under the auspices of the Department of Environment, to carry out joint exercises on the River Dnieper and some tributaries. This paper reports the results of selected methods used by the British side when applied to the conditions found in the River Dnieper.

Ecological indicators of water quality in small rivers

At the present time hydrobiological indicators are widely used for the control of surface water quality. Results of the applying of methods suggested at the 1st Soviet-American seminar (1975), development of improved methods and estimation of their usefulness for various conditions are presented in this report. Among the criteria permitting an estimation of the degree and character of changes in water quality and their connection with the functioning of river ecosystems in general, the biological tests of natural waters appears to be the most universal one and is being carried out in two main directions — ecological and physiological. This study summarises approaches in both directions.