Marine megafauna bycatch in swimming crab nets in northwestern Sri Lanka: a final report for Monterey Bay Aquarium Seafood Watch. Website: https://www.seafoodwatch.org/.
Ellen Hines, Gregory M. Verutes and Louisa Ponnampalam
Marine megafaunal bycatch, a major threat to sustainable populations, poses a particular challenge in developing countries. Yet, data to document bycatch and the effects of bycatch are often lacking in these countries as the research needed takes time, money, and training which are often limited. We have created an interdisciplinary and iterative approach that makes use of existing data and creates a framework for data acquisition that provides local practitioners and scientists the tools they need to conduct bycatch risk assessments. Our objective was to apply a suite of spatially explicit tools to assess the spatial exposure of dugongs, coastal cetaceans and sea turtles to incidental bycatch in the blue swimming crab (Portunus pelagicus) fishery in Palk Bay and the Gulf of Mannar in northwestern Sri Lanka. This research will contribute to the Seafood Watch Standard determination by developing guidelines for data collection for data-limited fisheries with respect to megafauna bycatch. To create the Bycatch Risk Assessment toolkit, (ByRA), we have consulted with scientists and local community members with expertise and/or experience with the animals at risk. Our team traveled to Sri Lanka to meet with agency experts and local scientists. In Palk Bay and the Gulf of Mannar, we met with community leaders and traveled to fishing villages, assessing net use spatially and temporally. From our observations and conversations, we have concluded that the exposure of marine megafauna to the crab nets is low, due to the placement and configuration of the nets. However, shark/ray nets commonly used by villagers, along with illegal commercial trawling close to coastal areas, are risky to all megafauna, and have a highly unsustainable bycatch of marine turtles. The ByRA outputs show that the risk of bycatch is directly associated with areas of fishing effort, especially shark/ray nets and illegal trawling, as well as some of the swimming crab net areas. For the dugong, most of this risk is in the Gulf of Mannar, in trawlers and shark/ray nets. For turtles, bycatch risk is mostly close to shore in all three nets. Olive ridley and leatherback risk is also high in swimming crab nets throughout Palk Bay. As uncertainty is quite high in this analysis, we caution that risk could be generalize and overestimated.