Potential bycatch impact on distinct sea turtle populations is dependent on fishing ground rather than gear type in the Mediterranean Sea: editorial comment on the feature article by Clusa et al. (2016)

...Within this broader context, the study by Clusa et al. draws together a range of techniques to consider the consequences of bycatch on the Atlantic and Mediterranean loggerhead populations sharing the same foraging grounds in the western Mediterranean Sea. Broadly speaking, they tested the hypothesis that juvenile turtles of Atlantic origin settle on the continental shelf later and at a larger size than their Mediterranean counterparts and hence may be more vulnerable to pelagic fishing gears. By using a combination of morphometric, stable isotopic and molecular data, the authors were able to evaluate the make-up of sea turtle bycatch from drifting longlines and bottom trawl/trammel nets around eastern mainland Spain, southern Balearic Islands, and southern Italy. Intriguingly, the population make-up of loggerhead bycatch reflected the area where the fishing operations were conducted but not the fishing gear used, against the original hypothesis of differential capture in demersal and pelagic fishing gears. Within a regional conservation framework, the take-home message was that the impact of loggerhead bycatch throughout the Mediterranean Sea will depend not only on the total number of individuals removed from the system, but also on the geographic distribution of the fishing effort. Consequently, this study was not merely a rerun of what had gone before but in a different area, but a well thought out amalgamation of techniques that highlighted the complexity of the sea turtle bycatch in near-shore environments where individuals from different age groups and natal sites may reside. ...