Production biology of the upland bully Philypnodon breviceps Stokell in a small Canterbury lake

Abstract

The purpose of this thesis was to investigate the relationships between food intake, biomass and production of a population of the upland bully, Philypnodon breviceps Stokell, in a small Canterbury lake. Early studies of fish populations were confined essentially to descriptive aspects of a species' biology (food habits, growth, life history and reproductive biology). However the inadequacy of this type of information for a complete understanding of the ecology of a fish population, particularly with respect to management of fisheries, was soon realised (Ricker, 1946), and in recent years increasing emphasis has been placed on the more functional aspects of aquatic ecosystems. This approach has been stimulated by the early contributions of such workers as Thienemann (1926) and Elton (1927), who first introduced the concepts of trophic levels, ecological niches and ecological pyramids. With the application of the laws of thermodynamics to ecological theory at about the same time (for example, Lotka, 1925), it became possible to consider the dynamic processes associated with the flow of energy through successive levels of a food chain. This trophic-dynamic approach was clearly outlined in the classic paper of Lindemann (1942), which provided a basic model for subsequent research in ecological energetics.