Basin-wide estimates of loggerhead turtle abundance in the Mediterranean Sea derived from line transect surveys

Loggerhead turtles are a globally vulnerable species of marine turtle. Broad-scale patterns distribution and abundance can provide regional managers tool to effectively conserve manage this at basin sub-basin scales. In study, combined aerial shipboard line transect survey data collected between 2003 2018 were used estimate throughout the Mediterranean Sea. Approximately 230,000 linear kilometers effort, from seven different surveying organizations incorporated into generalized additive model relate loggerhead density on segments environmental conditions. Two spatial models estimating density, abundance, generated – one long-term annual average covering 2003-2018 another summer 2018, when basin-wide survey, Agreement Conservation Cetaceans Black Sea, Sea Contiguous Atlantic Area Survey Initiative, was performed. Both adjusted for availability bias using dive tagged with time depth recorders. Mean estimated as 1,201,845 (CV=0.22). The 789,244 covered smaller area than average. These estimates represent first in not based demographic models. predicted similar distributions, higher northern Adriatic central basin, Tyrrhenian south Balearic Islands. Lower densities eastern Aegean highest areas generally did coincide previously established adult turtle foraging areas, which typically neritic, indicating predominantly predicting oceanic where most effort occurred. Juvenile comprise population, but care must be taken these they may accurately predict neritic subadult loggerheads often found. Despite limitation, major step forward conservation planning understanding species.