A preliminary methodology to characterize gillnet fleets in the Indian Ocean using satellite imagery: a case study on Pakistan
Brianna Elliott, Jeremy Kiszka, David W. Johnston, Marguerite Tarzia, Muhammad Moazzam, Hamera Aisha, Umair Shahid, Andrew Read
Current dataon cetacean bycatch in the Indian Ocean is extremely limited, but available information suggests that bycatch rates in gillnets may be unsustainable for some species, particularly in drift gillnets. Many drift gillnet fleets operating withinthe Indian Ocean Tuna Commission (IOTC) area of competence are comprised of relatively small vessels and are poorlydocumented by national management agencies. This contrasts with purse seine and pelagic longline fleets operating in this region, for which targetcatchesand bycatchesare relatively well documented. To help address knowledge gaps regarding the drift gillnet fleet, we are working to obtain information on drift gillnetvessels fromseveral IOTC Contracting Parties, particularly those fisheries occurring in the northern Indian Ocean: Oman, Pakistan, India, Sri Lanka, Indonesia, and Iran. We proposeto develop preliminary estimates of the size of the tuna driftgillnet fleet in these countries by using satellite imagery and machine learning to count vessels in relevant ports, characterize the fleet, and assess spatial distribution. Using independent estimates of bycatch and catchdata reported to IOTC, we hopeto create bycatch estimates for the fleets, where possible.Our efforts are in the early stages, and we are currently focused on fine-tuning our specific questions to answer with the satellite imagery and machine learning workflows. We seek feedback on our proposed methods to:1) better understand the drift gillnet fleet in the Indian Ocean, particularly in regions where large drift gillnet fleets are known to operate;and 2) gauge feasibility, pitfalls, and areas for collaboration for the proposed methodology, particularly the analysis of satellite imagery to characterize gillnet fleets. Our work is relevant to both the IWC Bycatch Mitigation Initiative and to the work of the IOTC’s Working Party of Ecosystems and Bycatch. We plan to combine this new information on fleet size and operation with a concurrent gap analysis of information on cetacean bycatch in these countries to characterize cetacean by-catch in these countries. We hope this work will assist the IOTC and IWC BMI in meeting some of their agreed steps following a joint meeting in September 2020.