Quantifying teleost discards in the shark fisheries of Western Australia.

Abstract

Quantifying discards is essential for assessing the impact of fisheries on non-target species and the ecosystems in which these fisheries operate. In Western Australia (WA), fishers are required only to report catches of retained species. For the currently operating shark fisheries of WA, the authors quantified catch time series of discarded teleosts using data from at-sea observers collected since 1993. Sixty-two teleost species were observed in the catch of which 20 were routinely discarded. The most commonly discarded teleosts were western buffalo bream/silver drummer, Kyphosus cornelii/K. sydneyanus, and dusky morwong, Dactylophora nigricans. Annual discards peaked in the 1990s; nonetheless, current discard levels, 36.9 ± 2.1 (S.E.) t year-1 , are much lower than the overall annual retained catches (c. 1000 tyear-1 ). The catch time series reconstructed in this study are important inputs for assessing the ecosystem-based approach used for managing WA's shark fisheries.