Seasonal niche and spatial distribution modelling of the loggerhead (Caretta caretta) in the Adriatic and Ionian seas

Abstract

Although Caretta caretta is the most common turtle in the eastern Mediterranean Sea, its distribution is relatively difficult to assess due to the lack of data in offshore waters. The ecological niches in the central‐southern Adriatic Sea and the north‐eastern Ionian Sea were investigated for loggerhead turtles with body sizes ≥20 cm during two periods: winter (W), which includes months from October to March, and breeding–nesting (BN), from April to September. Differences in the spatial distribution of loggerheads were explored between periods, and the environmental predictors driving habitat selection were examined. Loggerheads mainly select habitats within the continental shelf (<200 m) differently, and exhibit: (i) a generalist behaviour in the Adriatic subregion during BN and a specific selection of environmental conditions during W; and (ii) a specialist behaviour in the Ionian Sea. The Adriatic niche appeared as an important foraging ground year‐round, whereas the distribution of suitable areas in the Ionian Sea is patchy and limited to specific habitats close to shore. Extreme values of sea surface temperatures (SSTs) from October to March (W) influenced loggerhead distribution differently in the subregions: areas experiencing cold and warm SST peaks were selected, respectively, in the Adriatic and Ionian subregions. Moreover, SST in April largely contributed to defining the habitat suitability in BN for both subregions This study further confirms the importance of the Adriatic and Ionian seas for the conservation of loggerhead sea turtles and the need for seasonal investigations to establish effective conservation measures. Here, the use of a cost‐effective method (fixed line transects from ferries) to inform the distribution of sea turtles in offshore waters is a valuable methodology for long‐term seasonal investigations of the habitat use of sea turtles.

Environmental and pathological factors affecting the hatching success of the two northernmost loggerhead sea turtle (Caretta caretta) nests

“…The two turtle nests hereby described, the episodes reported in Marche Region (Pesaro) in 2019, and the two in Liguria (Finale Ligure in 2021 and Levanto in 2022), as well as the confirmed increase in sea temperature in the Adriatic basin 26 , 27 contribute to strengthen the hypothesis of the nesting activity expansion toward the northern coastline of the Western Mediterranean in the period 2010 – 2020 2 , 24 . In this context, Jesolo Lido and Scano Boa can be considered the northernmost nesting sites in the Mediterranean Sea ever monitored and, most likely, worldwide 28 .…”

Testing indicators for trend assessment of range and habitat of low-density cetacean species in the Mediterranean Sea

“…This was particularly the case for the WMED Subregion, and especially during recent years when new monitored transects also covered the westernmost portion of the basin, the Alboran sea and the Strait of Gibraltar area (roughly 80% of WMED covered by the effort). In the Adriatic Subregion, the effort strategy resulted in coverage of almost the whole region although with still some uncertainty in the northernmost area, as also assessed by Zampollo et al (2022). The Central MED was instead only represented by the effort in the eastern Sicilian coast and the Greek Ionian portion, and no effort was performed in the Aegean-Levantine Subregion, which leaves open opportunities for improvement.…”

Ocean highways in the Western Mediterranean: Which are the areas with increased exposure to maritime traffic for loggerhead turtles?

“…We acknowledge that the analysis of loggerhead turtle distribution implemented in this study did not account for the interannual environmental variability. Other approaches such as ecological niche and spatial distribution modeling (Melo-Merino et al, 2020;Smith et al, 2020;Chatzimentor et al, 2021;Zampollo et al, 2022) should be enhanced to further investigate the distribution of this species in the area in response to environmental variables (i.e., sea surface temperatures, chlorophyll-a concentration, distance to seamounts, bathymetry, etc. ), in order to identify mechanisms and variability in habitat utilization, and to predict future distribution patterns.…”