Loggerhead sea turtle bycatch data in artisanal fisheries within a marine protected area: fishermen surveys versus scientific observations

Loggerhead sea turtles can be incidentally captured by artisanal gears but information about the impact of this fishing is inconsistent and scarce. Recent studies have observed that the bycatch, or incidental catch rate, in fishermen surveys is irregular. The aim of this study was to compare direct data (onboard observers) concerning the incidental catch of loggerhead sea turtles by the artisanal vessels versus data from fishermen surveys. The study area was the Cabo de Gata-Níjar marine protected area, situated in the western Mediterranean (southeast of the Iberian peninsula). We observed two loggerhead turtles that were incidentally caught in a total of 165 fishing operations. According to fishermen surveys, a total of nine loggerheads were incidentally caught in 861 fishing operations. The differences between the loggerhead sea turtle bycatch reported by fishermen surveys and scientific observations versus random distribution (x2 = 0.3146, P = 0.575, df = 1) were not significant. We conclude that the surveys are useful but that findings should be interpreted with caution.