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Demand for Fish Swim-bladders Driving Inshore Dolphin Populations in Papua New Guinea Towards Local Extinction

Isabel Beasley , Yolarnie Amepou, Joyce Mavera, Wilma Mavea, Jim Anamiato, Karen Baird, Anissa Lawrence, Cara Masere

Abstract

Context. This paper investigates the unsustainable by-catch of inshore dolphins in gillnet fisheries targeting fish for swim-bladders in the Kikori Delta of southern Papua New Guinea. Methods. A carcass recovery program was undertaken from November 2021 to May 2022 using Community Dolphin Monitors. The Potential Biological Removal approach was used to estimate the sustainability of the level of mortality. An overview of four by-catch mitigation options previously trialled for other endangered small cetaceans was undertaken. This paper investigates the feasibility of applying these methods in Kikori based on the social, political, geographic and economic situation in Papua New Guinea. Key Results. A total of 72 cetaceans were found stranded, or by-caught in gillnets. These 72 mortality reports consisted of 69 Australian snubfin dolphins, two Australian humpback dolphins, and one pygmy sperm whale. The Potential Biological Removal suggested that the rate of by-catch for inshore dolphins is unsustainable and will contribute to the decline of these populations. Conclusions. The Potential Biological Removal suggests that inshore dolphin populations are quickly declining in the Kikori Delta. The three by-catch mitigation strategies that were determined to be potentially feasible to trial were: community-managed protected areas, acoustic devices (pingers), and gear modifications through acoustically reflective nets. However, because of the significant known by-catch, community-managed protected areas with no gillnetting should be the priority. Implications. The swim-bladder fishery is driving inshore dolphins towards extinction in the Kikori Delta. The fisheries are very lucrative, which places additional pressures and constraints on conservation and management programs.

PC23060  Accepted 02 May 2025

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