A local synecology of a marine system: studies on a demersal fish assemblage, Moreton Bay, Queensland

Abstract

A synecological study was made of a demersal fish assemblage in Moreton Bay, Queensland in order to explain an inter-related set of questions about the assemblage, best summarized as 'Why are there so many kinds of animals?' The assemblage was chosen because in some of its critical characteristics it was similar to a large class of systems including many ecosystems and because it existed in a fairly simple environment. The assemblage was sampled by trawling within one small restricted area only. This consstrained the study to be a local or within-habitat one rather than a comsparative or between-habitat one. This choice, and the choice of individsual organisms rather than energetic measures as the fundamental units of the study, are defended within the context of the general epistemological problem of mapping holistic systems into reductionist universes. These considerations suggested an analytical strategy which was adopted here - a set of independent partial 'holistic analyses of the assemblage whose intersections generate a theory explaining the system's behaviour. The whole system analyses are couched in reductionist terms and are multisvariate techniques - principal component analysis, canonical variate analysis, stepwise multiple linear regression, classification, and a suite of partitioned information-theoretic statistics. The theory generated from the intersections of these analyses emphasizes the hierarchical nature of the system, the importance of functional levels above the species and the coupling and optimization of adjacent functional levels in maintaining the system at a high level of diversity in a simple environment.