Caprera Canyon: A Hotspot Of Oceanic Biodiversity In The Mediterranean Sea

Jenn Hoskins
10th July, 2025

Caprera Canyon: A Hotspot Of Oceanic Biodiversity In The Mediterranean Sea

Striped Dolphin (Stenella coeruleoalba), one of the species mentioned.

Photo adapted from: harum.koh / CC BY SA (Source)

Key Findings

  • A 9-year study in the Caprera Canyon off Sardinia confirmed it as a vital hotspot for whales and dolphins, hosting 8 species with unusually high numbers, especially for Cuvier's beaked whales
  • This canyon is a crucial breeding and feeding ground for most observed species, including several endangered ones, underscoring its vital ecological role for marine life
  • The findings strongly support designating the Caprera Canyon as an Important Marine Mammal Area (IMMA) to protect this critical habitat and guide future conservation efforts
The Mediterranean Sea is a vital marine ecosystem, recognized as a global hotspot for marine biodiversity[2]. However, it faces significant threats from human activities, including overexploitation, habitat loss, pollution, and climate change, which are altering its delicate balance and impacting its diverse species[2][3]. Understanding the distribution and abundance of marine life, particularly vulnerable species like cetaceans (whales and dolphins), is crucial for effective conservation. Despite its importance, knowledge gaps persist regarding species distributions, especially in certain regions and for specific groups like cetaceans, where data collection has been historically uneven[4]. One such area, the Caprera Canyon, a deep underwater valley off Sardinia in the western Mediterranean, was suspected to be an important habitat for cetaceans, but detailed scientific studies were limited. To address this knowledge gap, researchers from the University of Minnesota conducted an extensive study[1] between 2011 and 2019. Their aim was to comprehensively describe the distribution, diversity, and relative abundance of cetaceans in the Caprera Canyon system. Over 216 boat-based surveys, covering more than 8,400 kilometers, were carried out using both dedicated research vessels and whale-watching boats. This approach allowed for a broad and consistent collection of data on cetacean sightings, their behaviors, and habitat use. The study confirmed the Caprera Canyon as a significant cetacean habitat, reporting a total of 810 sightings encompassing eight different species. These included the striped dolphin, fin whale, Cuvier’s beaked whale, sperm whale, Risso’s dolphin, common dolphin, bottlenose dolphin, and a rare sighting of Sowerby’s beaked whale. This represents seven out of the eight cetacean species regularly found in the western Mediterranean Sea, highlighting the area's high diversity. The overall Encounter Rate (ER), a measure of relative abundance indicating the number of sightings per 100 kilometers, was 10.6 sightings/100 km. Notably, the Cuvier’s beaked whale registered one of the highest ER values ever documented in the entire Mediterranean Sea, indicating its particular abundance in this region. Observations of calves and various behaviors, such as feeding and social interactions, suggest that the Caprera Canyon serves as both a breeding and feeding ground for most of these species. This multi-functional role underscores the ecological importance of the area. The presence of endangered and vulnerable species further solidifies the Caprera Canyon's status as a critical hotspot for cetacean diversity. The study also utilized habitat suitability models, specifically the maximum entropy (MaxEnt) approach, to predict areas where these deep-diving species might thrive. MaxEnt is a machine learning technique that uses environmental data from known species locations to predict suitable habitats across a wider area. These models indicated that other smaller canyons surrounding the Caprera Canyon could also provide suitable habitats, suggesting the importance of the broader submarine canyon system for cetacean populations. These findings significantly contribute to filling the data gaps previously identified in marine environments[4], particularly for cetaceans in the Mediterranean. While earlier research highlighted uneven survey coverage and a lack of data for the eastern and southern Mediterranean[4], this study provides detailed, systematic information for a crucial area in the western basin. The identification of the Caprera Canyon as a cetacean hotspot aligns with the understanding that the Mediterranean Sea, especially its western shelves, is a marine biodiversity hotspot with high concentrations of endangered, threatened, or vulnerable species[2]. The high impact of human activities across the Mediterranean, driven by factors like climatic changes, fishing, and shipping[3], makes the identification and protection of such critical habitats even more urgent. The Caprera Canyon study directly supports the need for spatial information on current impacts and the implementation of ecosystem-based management[3]. By identifying an area of high ecological importance, this research provides foundational data that can inform conservation efforts. The researchers emphasize that the Caprera Canyon and its surrounding areas could greatly benefit from being designated an Important Marine Mammal Area (IMMA). Such a designation would formally recognize the area's significance for marine mammals and could guide marine spatial planning, which is the process of organizing human activities in marine areas to achieve ecological, economic, and social objectives. This aligns directly with the call for coordinated management of key areas to improve the condition of marine ecosystems[3] and mitigate the growing threats of habitat degradation and climate change noted in broader biodiversity assessments[2]. The University of Minnesota's research provides invaluable baseline data for future studies on cetacean ecology and long-term population dynamics in the central-western Tyrrhenian Sea. By confirming the Caprera Canyon's role as a vital breeding and feeding ground and a hotspot for cetacean diversity, the study offers clear guidance for conservation strategies, aiming to protect these magnificent marine creatures and their essential habitats in an increasingly impacted Mediterranean Sea.

EcologyOceanographyMarine Biology

References

Main Study

1) The Caprera Canyon (north–eastern Sardinia): A hotspot of cetacean diversity in the western Mediterranean Sea

Published 9th July, 2025

https://doi.org/10.1371/journal.pone.0326426

Related Studies

2) The biodiversity of the Mediterranean Sea: estimates, patterns, and threats.

https://doi.org/10.1371/journal.pone.0011842

3) Cumulative human impacts on Mediterranean and Black Sea marine ecosystems: assessing current pressures and opportunities.

https://doi.org/10.1371/journal.pone.0079889

4) Assessing cetacean surveys throughout the Mediterranean Sea: a gap analysis in environmental space.

https://doi.org/10.1038/s41598-018-19842-9


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