Progress in addressing key research to inform Mobulid ray conservation in the Pacific Ocean (Paper + presentation)

Organisations - AZTI, ISSF & NOAA.

The habitat preference of mobulids for productive tropical and subtropical habitats, where tropical tunas also aggregate, increases their vulnerability to purse seine fishing. However, the rate of interaction of the purse seine fishery targeting tropical tunas with the different mobulid ray species has not been quantified in detail, especially in the western and central Pacific Ocean. One of the difficulties found to understand and quantify this interaction with accuracy is the identification of mobulids at the species level by the crew and observers onboard purse seiners. To evaluate the impact on mobulids it is also necessary to assess mobulid post-release mortality when applying safe handling and release methods. This project aims to address key research to inform mobulid species conservation with the collaboration of 12 purse seiners from the U.S. fleet. Sorting grids were constructed, to release the mobulids for each of the 12 purse seiners. Since June 2022, in total eight mobulas were released using Bycatch Reduction Devices (BRDs). Five mobulid tissue samples were collected for species identification through genetic analysis and three of them were also tagged with a Survivorship satellite Popup tag to study their survivorship after being released. Lessons learned from applying current protocols and practices will allow developing improved best practices to be implemented by the tropical tuna U.S. purse seine fleet which could be scaled up to other purse seine fisheries and nations in the longer term.