Ecological Risk Assessment of sea turtles to tuna fishing in the ICCAT region
Marine turtles spend the majority of their lives at sea; therefore understanding anthropogenic sources of mortality at sea is essential to assess population viability. This Ecological Risk Assessment assesses the risk to turtles from the impacts of tuna fishing in the ICCAT region. We used a Level 2 (semi-quantitative) assessment, within a Productivity-Susceptibility Analysis framework, at the Regional Management Unit (RMU) level; the assessment was hampered by significant data gaps and highly variable bycatch rate estimates. Bycatch rates were scaled to mean annual fishing effort, per RMU. ICCAT longline fishing poses the greater threat to turtles than purse seining. Loggerhead and leatherback turtles potentially encounter the most longline fishing effort (~300 million and >650 million hooks/yr, respectively). The east Atlantic olive ridley, the south Caribbean green turtle and SW Atlantic leatherback turtle RMUs were consistently among the most vulnerable from both gear types. Conversely, the west Atlantic olive ridely turtles showed lowest risk. Regions where turtles are at highest risk included S Caribbean and tropics (20°N-15°S, both gear types), and loggerhead turtles in the Mediterranean (longline only).