Self-reporting logbooks to collect seabird bycatch data: case study in the western Mediterranean Sea

Bycatch in fishing gear is the greatest threat to the survival of the critically endangered Balearic shearwater Puffinus mauretanicus, endemic to the Mediterranean and listed as ACAP priority population. But the numerous and highly diversified Mediterranean fishing fleet, mostly small-scale, makes it difficult to carry out a precise assessment of the problem using traditional methodologies of questionnaire surveys on port and on-board observations. Here a complementary methodology to assess bycatch is presented using self-reporting logbooks fulfilled by the fishers themselves on a daily basis and regularly monitored by a network of observers in the fishing ports. This approach was implemented by SEO/BirdLife between 2017 and 2021 in the western Mediterranean in Spain in which fishers from 42 vessels using demersal longlines collaborated by filling out logbooks monitored by eight observers at port. Data were collected from 3,522 fishing days in which 1,142 birds were caught, with shearwaters being the most affected (93%), with special relevance for Puffinus mauretanicus and P. yelkouan. Bycatch rates varied between years and areas and according to the configuration and operational characteristics of the gear, being more frequent in the small-scale fleet in late spring. The greatest risk of bycatch occurred when setting during the day, using small pelagic fish as bait, and adding little or no weight to the line. Self-reporting logbooks turned out to be a good method to assess seabird bycatch in small-scale fisheries with lower effort compared to observer programs and to raise awareness and involve fishermen in the finding of solutions to bycatch, showing promise for extension to other areas and gears, mainly in the small-scale fleet.