Elasmobranch bycatch in the demersal prawn trawl fishery in the Gulf of Papua, Papua New Guinea

W T White,A Chin,S A Appleyard,G J P Naylor,E Rochel,C A Simpfendorfer,B Sabub,L Baje

doi:10.1038/s41598-019-45715-w

Abstract

The elasmobranch bycatch of the Gulf of Papua Prawn Fishery is investigated in detail for the first time. Fisheries observers collected data on the elasmobranch bycatch from a total of 403 trawl sets (1,273 hrs) in the Gulf of Papua. A total of 40 species of elasmobranchs were recorded ranging in size from a 12 cm disc width stingray to a 350 cm total length sawfish. High mortality rates were recorded (>80%), attributed to the long trawl durations (up to 4 hours). The future inclusion of bycatch reduction devices would likely reduce the number of larger elasmobranchs being caught, based on evidence from the prawn trawl fisheries of northern Australia, and is being investigated by the PNG National Fisheries Authority. Differences in catch compositions were detected across the management zones as well as between the two monsoonal seasons (SE Monsoon and NW Monsoon). Increased monitoring and additional research is required and management plans should address the elasmobranch bycatch and in particular their high mortality rate.

Highlights

The majority of the global elasmobranch catch is incidental, in the form of bycatch from fisheries that target teleosts or crustaceans[1,2]
Trawling was concentrated in fisheries management zone 6 (n = 146 trawls), followed by zones 7 (n = 97 trawls) and 2 (n = 67 trawls), equating to 77% of all trawls being recorded from these three zones
The Gulf of Papua (GoP) prawn fishery only covers a relatively small proportion of Papua New Guinea (PNG)’s marine area, ~31% of the confirmed 130 elasmobranch species recorded from PNG13 were caught in this fishery

Summary

Introduction

The majority of the global elasmobranch catch is incidental, in the form of bycatch from fisheries that target teleosts or crustaceans[1,2]. Papua New Guinea (PNG) contributes only about 0.1% to the global tropical prawn catches, it is the only Pacific Island nation with a demersal prawn trawl fishery. Prior to the current study, no data existed on the elasmobranch bycatch of this fishery both in terms of catch composition and the fate of the bycatch following capture. Between 2014 and 2015, PNG’s National Fisheries Authority (PNG NFA) ran an observer program to investigate the elasmobranch bycatch in the GoP prawn fishery. The current study provides the first detailed investigation of this bycatch in PNG, including species, sex and size composition, and address the question of whether species richness and abundance varies at a spatial and temporal level. The major aim of this study was to provide management options to PNG’s NFA relating to the elasmobranch bycatch of GoP prawn fishery based on evidence-based science

Objectives

Methods

Results

Conclusion