A study of population changes, production and survivorship of river fish: results from a long-term student practical exercise

Abstract

The paper is presented in the form of a ‘case study’ of the changes in a fish population monitored over a period of several years. Fish from a 100 m section of a drainage canal in Suffolk, England were netted annually by undergraduate students as part of a practical exercise on fish population ecology. Data collected from 1981 to 1987 showed changes in the fish community both in terms of overall abundance (numbers and biomassj and in the relative abundance of different species. A variety of factors including human exploitation of the fish stock, the effect of biotic interactions and climatic conditions are considered as possible influences on fish recruitment and mortality. These possible explanations are examined against the background of other studies which have considered the causes of change in populations of freshwater fish.