Cetacean Sanctuary Research Ligurian Sea

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Research methods

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Presentation

The Ligurian Sea counts one of the highest concentration of whales and dolphins in the Mediterranean and as many as eight cetacean species are living there. Cetaceans - particularly the impressive fin whale - have become a symbol for the protection of this marine environment.

Research activities conducted by Tethys in the Ligurian Sea have led to the identification of a region critical to the habitat of several cetacean species. For example, this basin represents one of the principal feeding grounds for Mediterranean fin whales, a population that in recent years has been found to be genetically separate from it's Atlantic counterpart (another good reason for preserving it).

Unfortunately, the Ligurian Sea is also affected by severe anthropogenic impact, including pollution, heavy vessel traffic and intense fishing activities, providing significant threats to the survival of cetaceans.

Since 1989, the awareness of these problems has led Tethys to put forward a proposal for the creation of a Marine Reserve in the Corso-Ligurian Basin, the "Project Pelagos". After years of lobbying by Tethys and other environmental organisations, the Governments of Italy, France and Monaco got together in 1993 and signed a joint Declaration for the creation of a Mediterranean Sanctuary for Cetaceans. The agreement was finally ratified in 2003, and although to this day the area has seen little change in terms of management, the agreement represents an important step forward towards the final goal of ensuring protection to cetaceans living in the area.

In the meantime several internationally renowned institutions have emphasised the importance of the Sanctuary, including the World Conservation Union (IUCN), the Bonn Convention on migratory species, and the newly-born Agreement on the Conservation of Cetaceans of the Mediterranean Sea, Black Sea and Contiguous Atlantic Areas (ACCOBAMS). The Sanctuary has also been added to the list of Specially Protected Areas of Mediterranean Importance (SPAMI), created at the Barcelona Convention in 1999. This makes the Ligurian Sea Cetacean Sanctuary the first and only high seas protected area in the world.

In order to provide a scientific basis for management recommendations to the policy makers, the final goal of Tethys' research in the Sanctuary is the basic understanding of this extremely complex ecosystem. Intense research activities conducted by Tethys in this region have also been raising remarkable public awareness. Since 1992, almost 2,000 volunteers have participated in the cruises dedicated to Tethys' cetacean research. Living on board for many days and co-operating to the different phases of the research creates a bond between researchers and volunteers, transmitting to the latter a committment for environmental conservation.

Research carried out in the Cetacean Sanctuary by the Tethys Research Institute includes the study of cetaceans in the two main habitats: continental slope and offshore waters. Research focuses on the spatial distribution, habitat preferences, ecology and behaviour by all cetacean species living in the Sanctuary.

The research described above is conducted by means of field techniques including individual photo-identification, remote tracking, acoustics, distance sampling, behavioural sampling, remote sampling of skin biopsies, mark-recapture analyses and the use of time-depth recorders.

Project location

Our study area lies in the Pelagos Sanctuary and covers about 25,000 km2, including the waters between Genoa, the islands of Porquerolles and Cape Corse on the island of Corsica.

CSR study area within the Pelagos Sanctuary

While most of the Mediterranean is considered an oligotrophic sea, the western Ligurian Sea is characterized by high levels of primary productivity, caused by the interplay of climatic, oceanographic and physiographic factors. A dominant cyclonic (counterclockwise) current, flowing north along Corsica and Tuscany and thence hugging the coast of Liguria and mainland France in a westerly direction, creates a permanent frontal system which separates coastal and offshore waters. Intense biological activity is generated along this water mass boundary by the enhanced productivity and retention associated with this frontal system.

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Remotely sensed sea surface temperature (SST) during October 2006, in agreement with the frontal system (©Nasa)

Such phenomena are intermittently and seasonally reinforced by vertical mixing and coastal upwelling, generated by the prevailing north-westerly wind ('mistral'), which pumps deep nutrients and other organic substances contributed by rivers, most notably the Rhone, into the euphotic zone, where they fertilize growing phytoplankton populations.

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Remotely sensed chlorophyll a concentration in the Mediterranean Sea during April 2003 colour -coded to highlight different productivity levels (©Nasa)

Research methods

From 1990 to 2007, over 178,700 Km were travelled during 2,192 days spent at sea.

Visual and acoustic surveys were conducted on a daily basis. All the navigation data (position, speed, course), environmental data (sea state, weather, visibility, cloud coverage) and qualitative acoustic data (acoustic pollution and cetacean vocalizations by listening on the towed hydrophone array) were recorded. Human activities were also monitored (counting all types of boats, ships and fishing gear in a radius of 3 nm from the ship), and the presence of other marine animals (including sea turtles, tunas, mobulas, rays, swordfish and seabirds) were reported. Geographic position, movements, group size and composition of the cetaceans were also recorded during long-lasting observation sessions.

The various nature of the questions investigated by this study requires a multidisciplinary approach, thus entailing the use of a wide range of techniques.

Photo-identification enables researchers to recognise individual animals by taking pictures of their morphological features like the profile of dorsal fins or scars on their body. A photoID-based monitoring programme provides crucial information on cetaceans' distribution, habitat use, population estimate, social structure, seasonal presence, movements and association patterns.

Vocalisations and acoustic data are used to detect and follow the animals by means of a towed hydrophone array. The concurrent collection of behavioural data is aimed at assessing the functional meaning of the animals' sounds.

Behavioural study and respiration patterns, collected according to a dedicated protocol, enable to gain important information about different aspects of the animal's biology and about their interactions with human activities.

Skin swabbing: skin cells from some dolphins species are collected by "touching" them with a special sponge on top of a pole. By the DNA, genetic variability of the population, individual gender, population inbreeding, kinship patterns, and social structure can be assessed. From some species, like striped dolphins, skin and blubber samples were remotely collected. Blubber samples were used to determine concentrations of man-made contaminants, like polychlorobiphenils (PCBs).

Remote underwater tracking: velocity-time-depth recorders (v-TDRs), are attached to cetaceans by means of a suction cup. This very sophisticated technique allows to obtain diving profiles and to record maximum depth reached, swimming speed couples with environmental data.

Passive tracking of fin whales along the water surface are recorded by means of a laser range-finder, a GPS, and a dedicated software, with the concurrent timing of respirations. This technique is used to assess and quantify fin whales' reaction to anthropogenic disturbance.

Faecal sampling is occasionally performed at the water-surface with the aim to investigate feeding habits of the species. The analysis of fin whale faeces showed the almost exclusive presence of a small planktonic crustacean considered as the main prey species for fin whales in the Ligurian Sea while the analysis of sperm whale faeces provided the first insight of the diet for sperm whales in the Mediterranean Sea.