Unsustainable inshore dolphin by-catch in gillnet fisheries in the Kikori Delta, Papua New Guinea: a lucrative swim-bladder fishery causing marine megafauna population declines
Isabel Beasley, Yolarnie Amepou and Wilma Mavea
The Australian humpback dolphin (Sousa sahulensis) and Australian snubfin dolphin (Orcaella heinsohni) are both found in the Kikori Delta of Papua New Guinea. Both species are listed as Vulnerable by the IUCN Red List. The Kikori Delta is the only location that these species are found in the Pacific Islands, with small populations previously thought to number approximately 100-200 individuals respectively. By-catch of inshore dolphins in Kikori Delta subsistence gillnet fisheries was previously known to occur based on field trips to estimate dolphin abundance conducted in 2013 and 2015. A subsequent field trip in 2019 discovered that inshore dolphin by-catch levels had increased significantly resulting from a newly developed fishery targeting fish swim-bladders for Chinese medicine. During field trips to the Delta in 2020, researchers uncovered by-catch rates of at least 3-4 dolphins/month. A Kikori fisher can earn at least PGK1000 (USD$300) from one good quality swim-bladder. This one swim-bladder equates to more than a months salary, resulting in a fishery that is very difficult to manage. This situation parallels the dire situation facing the Critically Endangered Vaquita (Phocoena sinus) in the Gulf of California. This small porpoise has been pushed to near extinction by an illegal fishery for swim-bladders of the Critically Endangered tototaba fish (Totoaba macdonaldi). This paper describes a recent field trip to the Delta to establish a community dolphin monitoring program, where between 18 November 2021 ? 31 January 2022 a total of 13 snubfin dolphins were recovered by the carcass recovery program, eleven of these dolphins were confirmed to have been by-caught in large-mesh gillnets (5-7 inch nets). This paper highlights the need for urgent collaborative action (i.e. research, community/government consultation, and by-catch mitigation) to reduce dolphin mortalities as a matter of priority.