CETAMED NORTE: aerial and acoustic censuses of cetaceans and turtles in the north sector of the Mediterranean Cetacean Migration Corridor


The CETAMED NORTE project aims to increase knowledge on the distribution and abundance of sea turtles and cetacean species, as well as marine debris, found in the northern area of the Mediterranean Cetacean Migration Corridor.

The CETAMED NORTE project is supported by the Fundación Biodiversidad (Biodiversity Foundation) of the Ministry for the Ecological Transition and the Demographic Challenge (MITECO) under the Recovery, Transformation, and Resilience Plan (PRTR) funded by the European Union – NextGenerationEU. It is also in line with the goals of the LIFE INTEMARES project, coordinated by the Fundación Biodiversidad of the Ministry for the Ecological Transition and the Demographic Challenge.

Work on a vessel during the maritime survey. Photo: SUBMON / Dani San Roman.

The project


The Mediterranean Cetacean Migration Corridor is a Marine Protected Area spanning 46,385 km2. These waters bear a high ecological value and are a vitally important corridor for the survival of cetaceans in the western Mediterranean. Notwithstanding, there is currently little information on the distribution or abundance of the species present in the north section of this Marine Protected Area.

In order to work to preserve these cetaceans, all of which are protected nationally and internationally to different extents, we must also learn the degree of impact of the different threats in the area. We currently know that the Mediterranean is one of the environments with the highest plastic waste pollution, and plastic waste is one of the greatest threats to marine life. However, we need quantitative studies on marine debris to properly assess this issue.

This is why the CETAMED NORTE project came about, in order to provide updated data to increase knowledge of the species and threats in the area. The project consists of two research surveys. One is aerial, with a light aircraft, and the other is maritime, with a vessel, in the northern area of the Marine Protected Area of the Mediterranean Cetacean Migration Corridor, using distance sampling methodology. 

In recent years, SUBMON has conducted different projects in areas included in the Mediterranean Cetacean Migration Corridor. Specifically, the AHAB project and the SCARS project. Both of these projects were supported by the Fundación Biodiversidad of the Ministry for the Ecological Transition and the Demographic Challenge and provided data on the distribution and abundance of the sperm whale and the striped dolphin, as well as data on the distribution and relative abundance of other species in the zone, using the same methodology that will be used.

Area of Study


The area of study for the CETAMED NORTE project falls under the Mediterranean Cetacean Migration Corridor zone, between the coasts of Catalonia and the Balearic Islands. Two areas of study were created: one for the aerial survey (with a light aircraft), spanning a total of 32,652 km2, and another for the maritime survey (with a vessel), limited to zones in the northern corridor that are more than 1,000 metres deep and span an area of 31,668 km2.  

These waters bear high ecological value and form a vitally important corridor for the survival of cetaceans in the western Mediterranean. This is the case, for example, of the fin whale (Balaenoptera physalus), which uses this area in its migration to other latitudes during the spring. Additionally, it is the habitat and feeding zone for many cetacean species, like the fin whale itself, the sperm whale (Physeter macrocephalus), the bottlenose dolphin (Tursiops truncatus), the striped dolphin (Stenella coeruleoalba), the common dolphin (Delphinus delphis), the Risso’s dolphin (Grampus griseus), the long-finned pilot whale (Globicephala melas), and the Cuvier’s beaked whale (Ziphius cavirostris). It is also the habitat of other ocean species like the loggerhead sea turtle (Caretta caretta) and different seabird species.

The northern area of the Mediterranean Cetacean Migration Corridor, which corresponds to the study area of the aerial survey of the CETAMED NORTE project.
Transectos marítimos CETAMED
Maritime transects of the CETAMED NORTE project.

Species present in the Mediterranean Cetacean Migration Corridor. 

 Striped dolphin  (Stenella coeruleoalba)

This is the most abundant species in the Mediterranean. It can grow up to 2.6 metres. This species has a distinctive colour pattern, with a lighter belly and darker grey back. It is known for three lines (stripes) that start at the eye and spread, one to the fin, and the other from the side of the body to the anal region, and lastly a shorter one that originates between the other two. This dolphin is distributed differently from the bottlenose dolphin, since it is mainly found along continental shelf and the open sea.

The Mediterranean sub-population is considered as “Least Concern” status on the IUCN Red List.

delfin listado cetamed submon

Bottlenose dolphin (Tursiops truncatus)

This is the most abundant coastal cetacean species in the Mediterranean Sea. It can grow up to 4 metres. Its colour varies from light to dark grey, with lighter colouring on the belly. Given their presence in coastal waters, bottlenose dolphins in the Mediterranean are exposed to a wide variety of human activities. Incidental mortality in fishing, depletion of prey caused by overfishing, habitat degradation, boat traffic, underwater noise, and the effects on health caused by pollution are important threats. The size of bottlenose dolphin groups varies from a few individuals to dozens.

The Mediterranean sub-population is classified as “Least Concern” on the IUCN Red List.

delfin mular cetamed submon

Common dolphin (Delphinus delphis

An average-sized dolphin (between 1.5 and 2.5 metres), with a black back, yellow front side and greyish rear side (creating a sketch reminiscent of an hourglass), with a falcate dorsal fin in the middle of the body, which can sometimes have greyish marks on the sides. This dolphin inhabits both coastal and ocean waters, with group sizes varying from a few individuals to several hundred.

The Mediterranean sub-population is classified as “Endangered” on the IUCN Red List.

Delfín común Natàlia Amigó SUBMON

Risso’s dolphin (Grampus griseus

Risso’s dolphin is an odontocete with a robust body, it is known for its grey colouring and many scar marks (the youngest individuals do not have scars; they acquire them with age when they interact with other individuals prey, and the seabed), a round head, and a large, tall, and sharp dorsal fin. Risso’s dolphins can grow from 2.8 to 4 metres in length.

This species prefers the deep waters of the continental slope, as well as submarine canyons, especially in areas with heavily sloped topography. Although considered a regular inhabitant of the Mediterranean, we know very little about this species. Its conservation status was recently raised to “Endangered” by the IUCN.

Calderón gris SUBMON cetamed

Long-finned pilot whale (Globicephala melas

A large-sized odontocete (between 4-6 metres), it is black except for the belly, where it has a sizable, white mark. It has a low dorsal fin that hangs backward, which is relatively large and located in the middle of the body. This species prefers the waters of the continental slope, and are found in groups ranging from 5 to 100 individuals.

There are two different populations residing in the Mediterranean: one in the Strait of Gibraltar, considered as “Critically Endangered,” and the other in the Alboran Sea and western Mediterranean, considered as “Endangered.”

Calderón común SUBMON cetamed

Sperm whale (Physeter macrocephalus

This is the largest of the odontocetes, growing up to 16 metres long. The sperm whale is mainly grey/dark brown and is known for its extremely large head, occupying 1/3 of the total length of its body. The triangle-shaped dorsal fin transforms into a small hump, followed by a series of protuberances. Its skin is normally wrinkled behind the head and on the sides. This species has an asymmetrical spiracle located on the left of the head near the tip, making it blow at a 45º angle toward the left. This makes for easy identification of this species from a distance. Another characteristic of this species is that, when it submerges, it lifts its tail from the water (part of the body used for photo identification). In the Mediterranean, we have seen that it prefers deep waters near the continental slope and submarine canyon areas. In the area of study, we observe solitary individuals or small groups of 2 to 3 individuals (male) or groups of females with young whales and calves.

The species in the Mediterranean is classified as “Endangered” on the IUCN Red List.


Cuiver’s beaked whale (Ziphius cavirostris

Cuvier’s beaked whale is the only species from the Ziphiidae family commonly found in the Mediterranean. This is a large odontocete (between 5 and 6.5 metres). The colour of its body varies with age, with the animals going from having a dark brown, brown-grey body to animals with a brown-yellowish colour pattern. Adult males have a great number of scars on their body. As they age, the head takes on a whitish colour. Its triangular dorsal fin is slightly falcate, located on the back third of the body. This species can be seen year-round. It prefers deep canyon waters and underwater hills, and are usually found solitary or in groups between 2 and 4 individuals.

The population in the Mediterranean is classified on the IUCN Red List as “Vulnerable.”

Zifio de cuvier SUBMON cetamed

Fin whale (Balaenoptera physalus

This is the second-largest whale species in the world, growing up to 24 metres in length. This species has an elegant, aerodynamic body with a V-shaped head. It has a high falcate dorsal fin, located approximately on the back third of the body. The fin whale has a distinctive colour pattern: the back and sides of the body are black or dark-brownish grey, and the belly is white. The lower jaw has a unique asymmetrical pattern. It is dark on the left side and white on the right side. This species blows vertically, to a height of between 4-6 m. The fin whale can be found on the Catalan coast during the springtime and the early summer months. The Mediterranean sub-population consists of at least 10,000 mature individuals. This population is continuously declining. In fact, the Mediterranean sub-population is classified as “Endangered” on the IUCN Red List.

rorcual cetamed submon



Linear transects are used, covering the entire area of study, both from light aircraft and from a vessel, using Distance Sampling methodology. 

Distance sampling

This is a standard method to estimate the population abundance of wild animals. Linear transects along the study area have been designed using the software DISTANCE 6.0 (Thomas et al, 2003) in order to attain the same likelihood of coverage in the entire area. The density estimation along the transect is calculated by detecting the perpendicular distances of groups of observed animals, thereby estimating the effective bandwidth on each side of the transect. After these results have been obtained, the estimated density to the entire area of study is extrapolated.

Photo Identification 

Most cetacean species have natural, long-lasting features that allow us to recognize each individual. The photographs of these morphological features (such as the back edge of fins or dorsal fins, tail, or scars on the body), allow to identify specific individuals. Photo identification provides crucial information on cetacean distribution, habitat use, population estimation, social structure, seasonal presence, movements, and relationship patterns. 

Thus, when a species that is object of study is sighted, the vessel leaves the transect (whenever possible) to approach the individual or individuals and take photographs to later study them. 

Photo identification work during the CETAMED NORTE project. Photo: SUBMON.
Data registration during the CETAMED NORTE maritime survey. Photo: SUBMON.
Modelo de avioneta con la que se realiza la campaña aérea. Imagen: SUBMON.
Model of light aircraft that will be used during the aerial survey. Image: SUBMON.

Aerial survey

The aerial survey allows us to sample cetacean species and sea turtles, and to collect data on marine debris of anthropogenic origin to see to which degree this debris threatens fauna inhabiting or migrating through this protected zone. This survey covers a vast area of study in a brief period of time, spanning up to 3,800 km.

For this survey, which took place between 24 April and 14 May 2023, a twin-engine light aircraft with bubble windows for observation will be used. The vessel navigates following the designed transects, during which the conditions data, as well as all information necessary on each sighting of animals and marine debris, is recorded.  SAMMOA software is used for data recording. 

Maritime survey

The maritime survey complements the aerial transects, travelling up to 2,500 km by conducting acoustic transects using a towed hydrophone array. This will detect deep-diving cetacean species, which are more difficult to detect through aerial surveys because of their length of dive.

This survey, which took place between 15 May and 22 June 2023, was conducted from a 15-metre-long catamaran equipped with a crow’s nest. Like the aerial survey, data regarding meteorological and oceanic conditions, as well as sighting and acoustic information, were recorded.

During the visual effort, two observers (from a team of 7) explore 180º in front of the vessel while sailing at an average cruising speed of approximately 6 knots. One of these observers is located in the crow’s nest, 7.5 metres above sea level, and the other on the deck, at 1.5 metres. They are equipped with 7×50 reticle binoculars.

The acoustic effort involves the use of a towed hydrophone array with three ceramic elements and 150 metres of cable. The recording chain takes place through a converter that converts the analogical signal to digital, as well as a computer, which uses PAMGUARD software so a specialized observer can view sound and interpret it. Once clicks are detected, the software estimates a possible location angle for the individual or individuals. 

Moreover, when a sighting occurs, the vessel leaves the transect to approach the animals so the team can take photographs for their photo identification. 

Catamarán con el que se realiza la campaña marítima. Imagen: Montagu.
Catamaran used for the maritime survey. Image: Montagu.


The CETAMED NORTE project has revealed that the northern section of the Mediterranean Cetacean Migration Corridor is a crucial area for the survival of cetaceans and sea turtles. The data gathered from the project is a valuable resource for identifying and implementing effective conservation measures to protect marine biodiversity in the area.


ECS Conference 2024

The SUBMON research team presents some of the results obtained during the CETAMED NORTE project at the 35th European Cetacean Society Conference in Catania.

You can find the posters we presented here:

Research Team

projecte AHAB

Carla A. Chicote

Head of the CETAMED project. Engineer, master’s degree in marine ecosystem management, master’s degree in oceanography, and post-graduate degree in GIS (Geographic Information Systems). She is project leader at SUBMON, has spent over 15 years working in the field of cetacean research and conservation, and is specialized in bioacoustics.

Natàlia Amigó SUBMON

Natàlia Amigó

CETAMED project technician. She holds a degree in biology and a master’s degree in environmental engineering. SUBMON project technician on projects related to the study and conservation of cetacean populations. During the past 10 years, she has been studying and working toward the conservation of cetaceans in Catalonia.

Dani San Roman SUBMON

Dani San Roman

CETAMED project technician. He holds an Ocean Sciences degree and a master’s degree in marine biology. Technician in the SUBMON’s projects department working on the study and conservation of cetaceans since 2020.

Lluis Cardona

Lluís Cardona

Adjunct Professor with the Department of Evolutionary Biology, Ecology, and Environmental Sciences at the University of Barcelona. His research is focused on biology, ecology, and marine megafauna management, a diverse group of species known for extended longevity, late sexual maturity, and low fertility.

Manel Gazo

Manel Gazo

Lecturing Professor with the Department of Evolutionary Biology, Ecology, and Environmental Sciences at the Faculty of Biology. He holds a doctorate in Biological Science, master’s degree in marine aquaculture, and master’s degree in Non-Governmental Organisation Administration and Management from ESADE. Most of his work is focused on the biology, ecology, and management and conservation of marine megafauna species and populations, especially sea mammals and elasmobranchs.

Jaume Pujalt

Jaume Pujalt

Owner and skipper of the Montagu vessel. Jaume is highly experienced with projects to study cetaceans that use Distance Sampling methodology, having worked on the AHAB and SCARS projects conducted by SUBMON.

Adrià Bernaus

Adrià Bernaus 

Second-in-command of the Montagu vessel.

Sara Fernández SUBMON

Sara Fernández

She holds a degree in Advertising and Public Relations and a post-graduate degree in Graphic Design. Head of SUBMON’S Communications Department.

Cristiana Scanu SUBMON

Cristiana Scanu

Social Media Manager with a degree in International Studies. She collaborates with SUBMON’S Communications and Marketing Department as Social Media Consultant and Community Manager.