Spatio‐temporal distribution is fundamental information for species of conservation concern, like sea turtles, that are threatened by anthropogenic activities at sea such as fishing. While coarse‐scale distribution information is available for several sea turtle populations, fine‐scale distribution informing on hot‐spot areas for spatial management is more difficult to obtain. Here a citizen science approach involving tourism boats was undertaken to investigate the spatio‐temporal distribution of the loggerhead sea turtle (Caretta caretta) in the Pelagie Archipelago, located in a major foraging area for this species in the Mediterranean and where high fishing‐induced mortality occurs. The study was designed to provide data of absence and total sampling effort, commonly under‐reported in citizen science studies, allowing comparison among zones and periods. This was complemented by reports from fishing vessels. Tourism boats reported 584 loggerhead turtle sightings during 1718 daily trips and fishing vessels reported 280 loggerhead turtles captured during 1040 fishing days. The results indicate a strong heterogeneous distribution in the Archipelago, with a low turtle occurrence around the main island, Lampedusa, where the highest human presence and activity occur. This may represent rare evidence of displacement behaviour of turtles that is worth further investigation. This also suggests that the current small marine protected area around Lampedusa has a low conservation impact. Zones with higher loggerhead turtle occurrence appear to be in the south and the west parts of the Archipelago, suggesting that spatial management would be possible when relatively small hot‐spots have been identified through specific surveys. This study shows the potential of citizen science for providing preliminary information to guide more demanding and specific investigations. Such an approach may tremendously and rapidly improve the current knowledge on fine‐scale sea turtle distribution in regions with a great extension of coastlines and intensive tourist activities, such as the Mediterranean.

We investigate for the first time allometric vs. non-allometric shape variation in sea turtles through a geometric morphometrics approach. Five body parts (carapace, plastron, top and lateral sides of the head, dorsal side of front flippers) were considered in a sample of 58 loggerhead turtles (Caretta caretta) collected in the waters around Lampedusa island, Italy, the central Mediterranean. The allometric component was moderate but significant, except for the plastron, and may represent an ontogenetic optimization in the case of the head and flippers. The predominant non-allometric component encourages further investigation with sex and origin as potential explanatory variables. We also reported the variation of marginal and prefrontal scutes of 1497 turtles, showing that: variation of marginals is mostly limited to the two anteriormost scutes, symmetry is favored, asymmetry is biased to one pattern, and the variation of marginal and prefrontal scutes are linked. Comparisons with other datasets from the Mediterranean show a high variability, more likely caused by epigenetic factors. Finally, conversion equations between the most commonly used biometrics (curved and straight carapace length, carapace width, and weight) are often needed in sea turtle research but are lacking for the Mediterranean and are here estimated from a sample of 2624 turtles.