Ingestion of marine litter by loggerhead sea turtles, Caretta caretta, in Portuguese continental waters

•Litter ingestion by loggerheads was assessed in the Portuguese continental coast.•Out of 95 turtles, 59.0% had ingested litter.•97% of the sampled animals presented < 5 g (dw) of ingested litter per individual.•Plastic was the most important category of ingested litter.•No relation between stranding season, cause of death or size with ingested litter

The accumulation of litter in marine and coastal environments is a major threat to marine life. Data on marine litter in the gastrointestinal tract of stranded loggerhead turtles, Caretta caretta, found along the Portuguese continental coast was presented. Out of the 95 analysed loggerheads, litter was present in 56 individuals (59.0%) and most had less than 10 litter items (76.8%) and less than 5 g (dm) (96.8%). Plastic was the main litter category (frequency of occurrence = 56.8%), while sheet (45.3%) was the most relevant plastic sub-category. There was no influence of loggerhead stranding season, cause of stranding or size on the amount of litter ingested (mean number and dry mass of litter items per turtle). The high ingested litter occurrence frequency in this study supports the use of the loggerhead turtle as a suitable tool to monitor marine litter trends, as required by the European Marine Strategy Framework Directive.