The Ligurian Sea: an ideal habitat for cetaceans
The Ligurian Sea, especially in its western part, reaches remarkable depths in a short distance from the coast. The continental shelf, which by definition extends from the shore to 200m deep, is in Liguria little expanded. From the continental shelf, following the slope, the seabed drops rapidly to up to 2000 bathymetric meters, where the pelagic environment begins. A series of factors influence the Ligurian Sea, such as the action of the mistral and tramontane winds, the currents and the winter water homeothermy, allow the water replenishment and the resulting rise in the surface of the nutrients, which in other seas remain mostly confined to deep waters. The contribution of these substances allows the growth of phytoplankton, which is at the base of the food chain and constitutes the nourishment of the zooplankton, which in turn is caught by fish, cephalopods and marine mammals. The Euphausiidae Shrimp Meganyctiphanes norvegica, is the primary food of the Common Rorqual also known as the Fin Whale (Balaenoptera physalus), which, along with six other species of cetaceans, regularly frequents the waters of the Ligurian Sea. The abundance of nutrition in high Tyrrhenian waters, creates one of the areas with the highest concentrations of cetaceans. Each of the species in the area has an ideal habitat, closely related to the depth of the bottom; we can thus distinguish coastal, slope and pelagic species. However, as there are no precise boundaries at sea, marine mammals can move freely and sometimes they can be seen in unusual areas.
The International Sanctuary for Cetaceans
On the 25th of November 1999, the governments of Italy, France and the Principality of Monaco signed an agreement that sanctions, the establishment of a supranational protected marine area in the Mediterranean Sea, called the International Sanctuary for Cetaceans. The area, which extends for 96,000Km squared includes the coastal waters and the pelagic area between the headlands of the Giens peninsula to the Fosso Chiarone in southern Tuscany as well as the Pelagos Sanctuary. It extends to the waters of some islands, including Corsica and northern Sardinia as well as smaller islands such as the islands of Hyères, Liguria, the Tuscan Archipelago and the Strait of Bonifacio. It's an area of sea where the presence of cetaceans is considered to be the highest in the whole Mediterranean, an essential habitat for their survival. The existence of whales and dolphins in the area has been known since ancient times; however, targeted and offshore studies and research were carried out systematically only from the early 1980s. The collected data allowed us to recognise the exceptional biological value of the Corso-Liguria-Provence Basin and the need for its protection.
The abundance of cetaceans in a relatively small area is a fact of considerable scientific and educational value, which implies responsible management choices are to be taken. In the world, many species of cetaceans risk extinction and have been dramatically reduced in number due to long-lasting and uncontrolled commercial hunting which was mostly in a ruthless manner. Currently, cetaceans are protected by various international agreements. Nowadays it has become unusual for a cetacean to be harpooned, but their life is seriously threatened by many other dangers which are still attributable to human activity. Even the cetaceans which are living in the Sanctuary area, where whaling has never been practised except at an occasional level, are threatened by several factors. The Mediterranean Sea is a basin cut by excessive naval traffic (with high risks of acoustic pollution, animal collisions and hydrocarbon spills) and surrounded by highly industrialised and densely populated nations, which drain into it pollutants full of considerable danger. Among the most harmful substances, there are chlorinated organics, DDTs and PCBs, which, together with heavy metals, accumulate in the tissues of marine organisms, causing mammalian alterations in the immune system and reproductive functions. The activities of whale watching tourism, if conducted without respect for animals, may represent additional negative factors, which must be covered by regulations for human activities in the waters of the Pelagos Sanctuary.
Cetaceans: A general outlook
These animals have had a long evolutionary process, which started about 60 million years ago, this process brought a group of land mammals to adapt themselves to aquatic life. The pelt that they used to have, was substituted by a layer of subcutaneous blubber, being more efficacious in protecting the animal from the cold of their new surroundings, and with the ulterior function as an energy reserve. Their skeleton received continuous adaptations, such as the loss of their hind legs and the transformations of the anterior fins. These changes occurred to the point where cetaceans are nowadays more similar to fish than to their ancestors. Something though has never changed: they have kept their mammal nature, and thus, to breathe, they have to return periodically to the sea’s surface. Another founding characteristic that has survived the evolutionary process is the nursing of their young, who remain with their mothers for some years after birth. To hunt for their food, Cetaceans have developed different strategies. Those that belong to the subspecies of the Mysticeti, or better known as baleen and rorqual whales, are equipped with a series of cornea sheets, provided with bristles, known as shutters,