Getting to the bottom of bycatch: a GIS-based toolbox to assess the risk of marine mammal bycatch

C Junchompoo,AF Johnson,C Peter,LS Ponnampalam,E Hines,L Vu,G Minton,RL Lewison,M Caillat,T Huynh,GM Verutes

doi:10.3354/esr01037

Abstract

Marine mammal bycatch poses a particular challenge in developing countries, where data to document bycatch and its effects are often lacking. Using the Bycatch Risk Assessment (ByRA) toolkit, based on InVEST open-source models, we chose 4 field sites in Southeast Asia with varying amounts of data on marine mammals and fishing occurrence: Trat province in the eastern Gulf of Thailand, the Sibu-Tinggi Islands and Kuching Bay, Malaysia, and Kien Giang Biosphere Reserve in southwestern Vietnam. These field sites have similar species of coastal marine mammals, small-scale and commercial fisheries, and support for research from universities and/or management. In Thailand and Kuching, results showed changing patterns of fishing and Irrawaddy dolphin Orcaella brevirostris habitat use across seasons, showing how bycatch risk could change throughout the year. Risk maps for dugongs Dugong dugon in peninsular Malaysia highlighted patterns of bycatch risk concentrated around a mainland fishing pier, and revealed high risk in a northern subregion. In Vietnam, first maps of bycatch risk for the Irrawaddy dolphin showed the highest risk driven by intensive use of gillnets and trawling gear. ByRA pinpointed areas of spatial and seasonal bycatch exposure, and estimated the consequence of bycatch on local species, providing managers with critical information on where to focus bycatch mitigation and meet new global standards for US Marine Mammal Protection Act and other international regulation (e.g. Official Journal of the European Union 2019; Regulation 2019/1241) compliance. The toolbox, a transferable open-source tool, can be used to guide fisheries management, marine mammal conservation, spatial planning, and further research.

Highlights

Fisheries bycatch, the unintended capture of nontarget species, has been recognized as the most serious threat to marine mammals for decades (Reeves et al 2013)
A rough estimate of marine mammal bycatch suggests an estimated 300 000 cetaceans are taken each year by fisheries globally (Read et al 2006)
The 2017 International Affairs and Seafood Inspection rule from the NOAA Office of International Affairs in the United States stipulates that seafood imports to the United States need to comply with Marine Mammal Protection Act (MMPA) regulations that require the monitoring and reduction of marine mammal bycatch (Federal Register 2016)

Summary

Introduction

The unintended capture of nontarget species, has been recognized as the most serious threat to marine mammals for decades (Reeves et al 2013). Fisheries bycatch of marine mammal species is poorly monitored or regulated, so impacts of bycatch on local populations are not well understood. Countries with relevant fisheries exporting to the United States have 5 yr from January 2017 to document their compliance. In many of these countries there are significant data gaps on marine mammal distribution and abundance and bycatch rates, especially in developing countries (Williams et al 2016, Johnson et al 2017). The MMPA rule and similar regulations from the European Union (e.g. European Union Council Regulation 2019/1241; Official Journal of the European Union 2019) have intensified the need for better data to monitor and report marine mammal bycatch and fisheries-related population impacts

Objectives

Methods

Results

Conclusion