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Loggerhead turtles and Mediterranean Marine Protected Areas

Dec 20, 2022

Assessing whether an endangered species visits the protected areas – or not – is an important indicator of their relevance. Tracking of loggerhead turtles in the Mediterranean Sea show that modifying and adding protected area would be necessary for their conservation.

Main photo: Nesting female tagged by night (source “Abalo-Morla S (2023) Habitat use and distribution of loggerhead sea turtle (Caretta caretta) in the Mediterranean Sea: Implications for marine planning strategies. PhD thesis. Universitat Politècnica de València – Gandia Campus”)

Marine protected areas (MPAs) are one of the protections taken to enforce conservation measures. In the Mediterranean Sea, 9.4% of the surface is currently legally designated as protected, mostly in the north of the western basin. This Sea concentrates both marine biodiversity and a large number of potential threats on conservation.

Marine turtles are among the threatened species, and difficult to protect since they travel long distances, crossing international maritime borders. The loggerhead sea turtle (Caretta caretta) is considered ‘Vulnerable’ by the IUCN at the global level, ‘Least Concern’ in the Mediterranean Sea.

We’ve mentioned a study on marine turtles’ use of MPAs (see How endangered species such as marine turtles use Marine Protected Areas?), but in the Mediterranean, few studies have been done, while the western basin is an important foraging area, and, as mentioned, MPAs are defined in this basin.

Analysing a large number of loggerhead turtles’ tracking

Argos satellite tracking data of 103 loggerhead sea turtles were used in the study. They were tagged at different life-stages and released in the western Mediterranean over the 2003–2018 period.

With those location data, a state-space model was used to estimate the home ranges and relative density estimations of the species in the Mediterranean Sea. Those processed data were then overlapped with the Protected Areas limits.

The monitored loggerhead turtles travelled mainly throughout the western Mediterranean, but not exclusively.

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Turtle trajectories and marine protected areas in the Mediterranean Sea

Turtle trajectories (in blue) and marine protected areas (in green) in the Mediterranean Sea. (from [Abalo-Morla et al., 2022])

The modelled locations show that 70% of the tracked turtles visited at least one location within a Protected Areas (30 % none) over tracks lasting on average 133 days. Those areas represented 60 of the Mediterranean MPAs (over 1,233 total in the Mediterranean at the time of the study, thus less than 5%). The turtles spent in average less than 15% of their tracked time within.

The number of turtles having visited or not a protected area depended largely on their life stage: half the late juveniles but less than 6 % of the post-hatchings never visiting one. On the 103 tracked individuals, only nine spent more than half their monitoring time within a MPA.

New or enlarged Marine protected areas are necessary in the western Mediterranean Sea for loggerhead turtles’ conservation

The loggerhead turtles thus spent very little time in protected areas, and in very few of them. Using the home range and core areas from the analysis enables to propose with new protected area, with an emphasis on measures minimizing threats to marine turtles. Connection between MPAs are also proposed, so that the protection of turtles during their travel is more continuous.

Protected Areas proposed by this study for loggerhead sea turtle conservation in the Mediterranean Sea

Protected Areas proposed by this study for loggerhead sea turtle conservation in the Mediterranean Sea: A) Alboran Sea, B) Algerian basin, C) Northern Strait of Sicily, D) Tyrrhenian Sea, E) Northeast Tunisia, F) Malta and G) Northern Ionian Sea. Current Marine Protected Areas are shown in green. In blue the density estimates from the model. Delimitation of countries Exclusive Economic Zones are in orange. (from [Abalo-Morla et al., 2022])

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  • Abalo-Morla S, Belda EJ, March D, Revuelta O, Cardona L, Giralt S, Crespo-Picazo JL, Hochscheid S, Marco A, Merchán M, Sagarminaga R, Swimmer Y, Tomás J. 2022. Assessing the use of marine protected areas by loggerhead sea turtles (Caretta caretta) in the western Mediterranean. Global Ecology and Conservation, 38, e02196.
  • Abalo-Morla S, Belda EJ, Tomás J, Crespo-Picazo JL, Marco A, Revuelta O. 2022. Satellite-tracking dataset of loggerhead sea turtles tracked from western Mediterranean. Data in Brief, 43: 108432

More information:

  • Abalo-Morla S, Marco A, Tomás J, Revuelta O, Abella E, Vicente Marco V, Crespo-Picazo JL, Fernández C, Valdés F, Arroyo MC, Montero S, Vázquez C, Eymar J, Esteban JA, Pelegrí J, Belda EJ. 2018. Survival and dispersal routes of head-started loggerhead sea turtle (Caretta caretta) post-hatchlings in the Mediterranean Sea. Marine Biology 165:51.