Demand for fish swim-bladders driving inshore dolphin populations in Papua New Guinea towards local extinction

Context By-catch in gillnets for fish swim-bladders (‘fish maw’) is driving dolphin populations to extinction in Papua New Guinea. Aims 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 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 From November 2021–May 2022, 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 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.