Fisheries Research Articles

Quantifying shark and ray discards in Western Australia’s shark fisheries

Document Type

Article

Publication Date

11-9-2021

Journal Title

Marine & Freshwater Research

ISSN

Print: 1323-1650 Electronic: 1448-6059

Keywords

Conservation, Elasmobranchs, Gill-net fishery, Management

Disciplines

Aquaculture and Fisheries | Marine Biology | Natural Resource Economics | Natural Resources and Conservation | Natural Resources Management and Policy | Population Biology | Survival Analysis | Sustainability

Abstract

Commercial fisheries can discard a considerable volume of sharks and rays, which, as a group, are of high conservation concern. In Western Australia (WA), commercial shark fishing commenced in the 1940s; however, catch time series are not available for discarded species. The present study quantified catch (i.e. dead individuals) time series of discarded sharks and rays in WA’s shark fisheries using on-board observer information collected since 1993 and testing assumptions through sensitivity analysis. Overall, 18 shark and ray taxonomic groups were discarded, comprising ~20% of the observed catch by number. Port Jackson shark, southern eagle ray and spurdogs were the most commonly discarded elasmobranchs, followed by western wobbegong, angel sharks, stingrays, and guitarfish and shovelnose rays. For the base case scenario, the catch of these species was small, peaking at 12.6, 5.6, 1.3, 1.8, 4, 1.3 and 2.7 tonnes (Mg) respectively, given their low post-release mortality (PRM). Current catch levels were even lower (e.g.shark). Other discarded elasmobranchs were rarely caught. Assuming 100% PRM resulted in higher annual catches, highlighting the need for further research on the PRM of sharks and rays. The reconstructed catch series will be used in risk assessments to determine the sustainability of discarded species.

Link to Full Text

Share

COinS
 

Digital Object Identifier (DOI)

https://doi.org/10.1071/MF21159