Fig 1.
(Top) Map of the Caprera Canyon and surrounding waters, with bathymetry represented by varying shades of blue and isobaths indicated. The nearby national/international parks are shown in light grey, and the Pelagos Sanctuary with a dotted area. (Bottom left) Location of the study area in the Mediterranean Sea. (Bottom right) Search effort tracklines offshore Sardinia 2011–2019, with overall tracklines (light grey) and on–effort tracklines (black = platform of opportunity; red = dedicated research vessels).
Fig 2.
Monthly survey effort (on–effort km) from 2011 to 2019.
Survey effort, represented as stacked bars, with different colours indicating contributions from each year. Survey coverage was highest during the summer months (July and August), with reduced effort in winter and early spring. The variability in effort reflects seasonal and logistical constraints associated with data collection.
Table 1.
Summary of sighting, survey and diversity data, including encounter rates (ER), group size, depth and slope relative to cetaceans in the Caprera Canyon waters between 2011 and 2019.
Fig 3.
Annual sighting frequency (%) of different cetacean species in the Caprera Canyon and adjacent waters from 2011 to 2019 (n
= 810, on–effort sightings). The overall sighting frequency for the entire study period (Total) is indicated. Species are represented by different colours.
Fig 4.
Interannual variability of ER (Mean
± SD) of the most common cetacean species. The regression line is fitted based on the means of the annual ERs.
Fig 5.
Maps showing location of the cetacean sightings off north–eastern Sardinia, throughout the study period (2011–2019) scaled by group size.
The nearby national/international parks are shown in light grey, and the Pelagos Sanctuary as a dotted area. Data shown in the maps are based on 1110 sightings, both ‘on–effort’ and ‘off–effort’. Striped dolphin (n = 604); Fin whale (n = 244); Cuvier’s beaked whale (n = 149); Common bottlenose dolphin (n = 79); Sperm whale (n = 15); Risso’s dolphin (n = 10); Common dolphin (n = 8) and Sowerby’s beaked whale (n = 1).
Table 2.
Results of the best fitting MaxEnt models. The values in the table represent the arithmetic mean of percent contribution and permutation importance. Higher values indicate greater variable importance.
Fig 6.
Habitat suitability maps and species richness.
Habitat suitability of (a) striped dolphin, (b) fin whale, (c) Cuvier’s beaked whale, (d) sperm whale. In the scale bar, index is continuous from very suitable habitats (value 1, dark blue) to very unsuitable habitats (value 0, white) for the species; (e) Spatial distribution of species richness, with a region around the Caprera Canyon system (lower slope habitat) of high diversity of cetaceans, where three or more species are present.