Ecological and fishing features of the Adriatic Sea
Abstract
For most of the tertiary age the Mediterranean was part of the Tethys Sea, that vast primaeval ocean. The current configuration of the Mediterranean was produced by the tectonic events that followed during the upper Miocene, Pliocene and Quartenary periods (R u g g e r i , 1967).
According to the most widely accepted theory, this intermediate ocean was largely open to the Indo-Pacific region and populated by a tropical type fauna (Paleomediterranean Element).
After the salinity crisis at the end of Miocene period (during the so-called Messinian period) due mainly to reduced intercommunication with the Atlantic and the closing of intercommunications with the Indo-Pacific (previously via Syria), the Mediterranean consisted of a series of lagoons.
A certain degree of irregular intercommunication was maintained with the Indo-Pacific through the north sea of Paratethys populated by a distinctly Sarmatic fauna, while the paleomediterranean fauna element was disappearing or being transformed as part of the Endemic Element, consisting of typical species of the Mediterranean. This geomorphological transformation and this process of speciation were completed during the Pliocene period. In the meantime the Mediterranean was gradually becoming a temperate sea, which still characterizes it today. Its intercommunications with the IndoPacific were closed definitely while those with the Atlantic were reopened. In this phase, the Atlanto-Mediterranean Element was introduced in the Mediterranean, which is to remain constant and constitutes the main element of the current populations.
During the events of the Quarternary period, with its alternating regressions (cold periods) and transgressions (hot periods), the Northern Element alternated with the Senegalian Element, which can be considered as a superimpression on the Endemic and Atlanto-Mediterranean Elements (Pérès et Picard, 1964). After the great post- Würmian deglaciation, the situation has remained fundamentally as it is today. The gradual increase in salinity has led to the extinction of almost all the northern species to reach the following fauna situation: the majority involving Atlantic-Mediterranean species (immigrated during the Pliocene) and endemic species (formed during the Calabrian and Sicilian periods). To these two numerically dominant groups it must be added the survivors of the Senegalian Element (which entered the Mediterranean during the Tyrrhenian period) and a number of survivors of the Northern Element (entered at Würm) (Pérès and Picard, 1964).
It is important to underline that the alternation of warm and cold fauna in the Mediterranean is not due to temperature variations but to the modifications of the flow of the currents in the Strait of Gibraltar and Bosphorus (Mars, 1963), which were in turn related to the climatic fluctuations of the glacial and interglacial periods which were in turn related to the climatic fluctuations of the glacial and interglacial periods which characterized the Quarternary period.
Regarding the Adriatic, several biogeographers and paleontologists retain that the last contact of the Mediterranean with the Indo-Pacific occurred through a corridor which connected Miocene and the Pliocene periods. The Sarmatic Sea collected in a vast basin the Black Sea, the Caspian Sea and the Lake of Aral, which were once also a part of the Tethys Sea.