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The reasons of the presence of cetaceans

That the sea comprised in the imaginary triangle whose apexes touch to east of the Tuscany, south the Corsica and the west the Blue Coast was unusually rich of marine fauna, and in particular of cetaceans, had been noticed by now from decades but the true reasons of a such abundance of life have been only of recent assumed with the succession of deepened searches and careful observations from part of marine biologist. 

Some time ago assumed quite that the great cetaceans could not live in a narrow sea therefore like the Mediterranean, if compared to the oceans, arriving to support quite that the sights of whales could regard passing animals or that they had mistaken broken off. Even if in truth the study of the cetaceans of the Mediterranean has been in the centuries much devoid one (often was limited only to beached animals). What instead has emerged from recent studies completed from the biologist has turned out to be amazing, not only not draft of animals that escapes from the oceanic routes for error, seems that in some cases the existence of a true one permanent population of cetaceans of the Mediterranean; from completed searches capturing champions of fat of these mammals it is uncovered that their DNA differs from that one of their oceanic cousinses or better has characterized one tightened relationship between all the Mediterranean animals. It can therefore be supported with reasonable certainty that the cetaceans that lives in this sea belong to it in all and for all and are not travellers who have mistaken road, even if the exchanges with the Atlantic Ocean are remarkable, as it demonstrates the fact that the presence, above all of the large cetaceans, in the part oriental of the Mediterranean river basin is more insufficient and gradually decreasing. Moreover it has been observed like the cetaceans of the Mediterranean adopt peculiar social behaviors, probably dictated from the narrowness of the river basin, the sparsity of predators and the lack of migratory requirements; immediately is possible to see the lack of large branches, often the animals are in meager groups or quite isolated or in brace; the riproduttive seasons vary also. The insufficient production of biomass from part of the organisms vegetables for deficiency of upward movements of the water of the Mediterranean does not characterize instead the western From Ligurian Sea, where it is a lot abundant, to oceanic levels. It appears by now strengthened that in this, relatively circumscribed, called portion of the Mediterranean From Ligurian Sea (from the name of the Italian region along whose coasts it breaks up) in determined periods of the year blooms one above all extraordinary marine wealth formed from microscopical innumerable animals of dimensions and variable characteristics (mostly Meganictyphanes Norvegica belonging to the Euphasiacean family such as the Euphausia superba present on the contrary in oceanic waters) but not larger than some centimeter; this called mass Krill and plancton constitutes the nutriment of many of the cetaceans, above all of large size, that pass great part of the own existence leaking tons of marine water in order to extract from it quintals of the precious one plancton. The period that goes from june to October sees to coincide the birth of the plancton with the arrival of the whales which is supposed passes the winter in the warmer waters in the south of the Mediterranean (or in the Atlantic Ocean). Which are the reasons for which just in the Ligurian Sea a such outbreak of microscopical life is taken place is not still sure. Sure the main characteristic of this portion of the Mediterranean is represented from the marine currents that with force and constancy guarantee a continuous water reciprocation; in truth but this enough not to justify one particularly high primary productivity regarding the found medium values in pelagic ambient of all western Mediterranean. Therefore one has assumed that the particular oceanographic and climatic conditions are fundamental which intense upward nourishing evaporation, contribution from the Rodano and movements of deep water (upwelling) in the course of which masses water that are in depth of 100. 200 m and rich of nitrates and phosphates they arrive in the eufotic layer. Recently has been taken to the attention of biologist one theory founded on the study of the so-called the "submarine rivers". They are true and own rivers of sweet water that runs from the mainland and arrives in sea but not on its surface, but in depth. Approximately it has been estimated that in order to measure the water amount that the submarine rivers pour in sea, it would be necessary to multiply for five that one that reaches from the rivers. There is therefore an enormous amount of sweet water that for the students of University of S.C. USA would influence remarkablly on the marine ecosystem and in particular on the life of the anomalous ones whose feeding is tied to the Krill and the plancton. In the Ligurian Sea in particular "an enormous sweet water blade cold submarine gushes out from the waters that, massive the Alpine one collects during the winter, slides under the Liguria and arrive, following the faults in the Northern Tyrrhenian sea. The cold, submarine, water blade arriving in abundance, in june because of melting of snows, rich of mineral salts comes in contact with that warmth, salata, with ionic exchange, development of bacteria, and forms the plancton where the cetaceans come to eat and to drink". (Prof Francesco Conterno).

The study of the cetaceans of the Mediterranean is still to the beginnings, but it is helped from the strong interest legacy to the safeguard of a marine ambient.



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