Read all about it: Multi-methods approach for estimating Irrawaddy dolphin bycatch

IMG_0835Officially out in Marine Mammal Science this month – another chapter from the ol’ disseration – Multi-methods approach to characterizing the magnitude, impact, and spatial risk of Irrawaddy dolphin (Orcaella brevirostris) bycatch in small-scale fisheries in Malampaya Sound, Philippines!

Email me to request a copy if you do not have access to Marine Mammal Science.


Addressing the urgent conservation threat of marine mammal bycatch in small-scale fisheries requires information on bycatch magnitude, gear types, population impacts, and risk. However, data on these proximate attributes are widely lacking in developing countries. This study used a multi-methods approach integrating boat surveys and interviews with fishermen (n = 526) to assess proximate attributes of bycatch for the Critically Endangered subpopulation of Irrawaddy dolphins (Orcaella brevirostris) in Malampaya Sound, Philippines. Given an updated population estimate of 35 individuals (CV = 22.9%), the estimated rate of bycatch fatalities exceeds the potential biological removal rate. Spatial overlap scores were calculated to characterize overlap between dolphins and fisheries as a proxy of bycatch risk. These scores identified particularly high risk areas that could be prioritized for gear bans. However, completely reducing bycatch risk would require more widespread bans beyond these high risk areas. Implementing gear restrictions will be immensely challenging, given serious obstacles to fisheries management at this site. The multi-methods approach describes the urgency of the bycatch problem and the changes required for mitigation, setting the stage for identifying and evaluating potential solutions. It can be readily applied to developing country sites to guide more efficient and complete data collection and conservation efforts.



I would like to thank the Associate Editor, Tim Gerrodette, as well as two anonymous reviewers for their comments. Many heartfelt thanks go to the Malampaya Sound research team: Ely Buitizon, Zion Sunit, Ricky Tandoc, Cristela Oares de Sena, Archie Espinosa, Romeo Borrega, and Eira M. Whitty. Grateful acknowledgements are due to the Protected Area Management Board, Palawan Council on Sustainable Development, the municipal government of Taytay, the provincial government of Palawan, and the study barangays for permission to conduct research in Malampaya Sound; to Alexander Mancio and the Protected Area Office, Marivic Matillano and WWF-Philippines, Lota Creencia and Gerlyn Supe at Western Philippines University, Hilconida Calumpong at the Silliman University Institute for Environmental and Marine Sciences, the Philippine-American Educational Foundation, and the Southwest Fisheries Science Center for logistical support and expertise; and to Louella Dolar for invaluable guidance. Lisa Ballance, William Perrin, Louella Dolar, Paul Dayton, and Ellen Hines provided constructive comments on draft manuscripts.


Permission to conduct research was granted by each barangay, the municipality of Taytay, the Protected Area Management Board, the Palawan Council for Sustainable Development, and the Provincial Government of Palawan. Institutional Review Board approval was obtained from the UC San Diego Human Research Protections Program for all interviews. Funding for this research came from the U.S. Marine Mammal Commission, National Geographic-Waitt Grants, the Small-scale and Artisanal Fisheries Network, and the Fulbright U.S. Student Program for the Philippines.

Website Built by

%d bloggers like this: