A systematic review protocol for quantifying bycatch of critically endangered leatherback sea turtles within the Pacific Ocean basin.

Background: The Pacific Ocean supports two leatherback sea turtle populations, each of which is Critically Endangered primarily as a result of ongoing incidental bycatch within small-scale and industrial fisheries. Conservation planning has included population viability analysis (PVA), which depends on accurate data on mortality and morbidity (sublethal effects) rates to yield realistic results that can inform management decision-making. Existing leatherback PVAs are based on best available data, however, estimates of mortality and morbidity rates are heavily influenced by estimates of bycatch. These, in turn, are based on unknown levels of observer coverage in many fisheries, estimated to be less than 1% coverage in some artisanal and industrial fleets. Leatherback population recovery depends on bycatch reduction. It is vital to understand the source, scope, and scale of leatherback bycatch wherever and whenever leatherbacks occur. Here, we outline a protocol for a systematic review to aggregate existing estimates of leatherback bycatch within the Pacific Ocean, on a population- and basin-level. These results will generate the first comprehensive estimate of leatherback turtle bycatch for any ocean basin and will be incorporated into future conservation planning for Pacific Ocean populations.

Methods: A Boolean search string will be input into several bibliographic databases to yield articles and grey literature (governmental, business, and industry information not controlled by commercial publishing) related to the research question. Additional grey literature searches, snowball sampling and expert elicitation will be used to create as robust and comprehensive a pool of literature and/or databases as possible. Retrieved articles will be reviewed for eligibility using the SPIDER search strategy tool (Sample- Phenomenon of Interest-Design-Evaluation -Research type; 7). Articles which meet the criteria will be included in the systematic review, and their data will be collated into comprehensive estimates of leatherback sea turtle bycatch within the Pacific Ocean, one for each population. These data will be further teased apart by fishery size, fishing gear type, fishing nation, fishery region, and fishery target species, to target management more directly. This information will be published and provided directly to stakeholders for use in conservation management.