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

• DOI: 10.3389/fmars.2023.1116829
• Publication Date: 2023-05-25T04:29:38Z
• Authors: Antonella Arcangeli; Fabrizio Atzori; Marta Azzolin; Lucy Babey; Ilaria Campana; Lara Carosso; Roberto Crosti; Odei Garcia-Garin; Martina Gregorietti; Arianna Orasi; Alessia Scuderi; Paola Tepsich; Morgana Vighi; Léa David
• Keywords: Species distribution; Marine protected area

Introduction Conservation of cetaceans is challenging due to their large-range, highly-dynamic nature. The EU Habitats Directive (HD) reports 78% species in ‘unknown’ conservation status, and information on low-density/elusive such G.griseus, G.melas, Z.cavirostris the most scattered. Methods FLT-Net programme has regularly collected year-round data along trans-border fixed-transects Mediterranean Sea since 2007. Nearly 7,500 cetacean sightings were recorded over 500,000 km effort with 296 less-common species. Comparing across two HD 6-years periods (2013-2019/2008-2012), this study aimed at testing four potential indicators assess range habitat short-term trends : 1) change Observed Distributional Range-ODR based known occurrence, calculated through Kernel smoother within area; 2) Ecological Potential Range-EPR extent, predicted Spatial Distribution Models; 3) Range Pattern, assessed as overlap shift core areas between periods; 4) changes ODR vs EPR. Results Most EPR confirmed persistence important sites, especially Western-Mediterranean. All species, however, exhibit distribution extent (contraction or expansion) an offshore shift, possibly indicating exploitation new avoidance more impacted ones. Discussion that could underestimate real occupied range, referring area only; it can be used detect providing spatio-temporal scale representative range. allows generalising outside area, defining species’ Habitat Occupied/Potential proportion. To investigate range-trends, needs adjusted also proportion larger than presence limiting factors, smaller, if anthropogenic pressures force ecological niche. Conclusion Using complementary proved valuable evaluate significance changes. concurrent analysis similar ecology was critical whether detected are species-specific broader trends. sampling strategy adequate for trend assessment Western-Mediterranean Adriatic basins, while transects needed characterize Central-Mediterranean Aegean-Levantine variability.