Prawn Fishery By-catch and Discards: marine ecosystem analysis - population effects

Abstract

In prawn trawl fisheries, the catch and discard of non-target species (by-catch) can have an impact on the ecosystem and species populations, particularly by the favouring of scavengers and removal of top predators. An understanding of the fished ecosystem, including species composition, abundance, catchability, and survival, is instrumental for the adoption of the principle of ecological sustainability and implementation of ecosystem-based management. The research reported here constitutes three separate studies, a) an ecological assessment of quantitatively dominant by-catch species using a consistent rigorous statistical approach for hypotheses testing applied to data sampled at five selected sites at the Spencer Gulf prawn fishing grounds with a history of different trawling intensities, b) a detailed assessment of physiological stress, and mortality of selected by-catch species during capture and handling, and c) a field and laboratory experimental study of movements and feeding behaviour of Port Jackson sharks during trawl operations.