The Mediterranean - Animal Life, Fisheries And Salt Pans
( Originally Published 1920 )
ANOTHER remarkable feature of the abyssal waters of the Mediterranean consists in their poverty of animal life. No doubt there is some life ; the dredgings of the Porcupine and the telegraph cables, which, on being brought to the surface, were found to be covered with shells and polypes, prove this. But, compared with those of the ocean, the depths of the Mediterranean are veritable deserts. Edward Forbes, who explored the waters of the Archipelago, arrived at the conclusion that their abyssal depths were entirely devoid of life, but he was wrong when he assumed an exceptional case like this to represent a universal law. Carpenter thinks that this absence of life in the depths of the Mediterranean is due to the great quantity of organic remains which is carried into it by the rivers. These remains absorb the oxygen of the water, and part with their carbonic acid, which is detrimental to animal life. In numerous instances the water of the Mediterranean contains only one-fourth the normal quantity of the former gas, but fifty per cent. in excess of the latter. To the presence of these organic remains the Mediterranean is probably indebted for its beautiful azure colour, so different from the black waters of most oceans. This blue, then, which is justly celebrated by poets, would thus be caused by the impurity of the water. M. Delesse has shown that the bottom of nearly the whole of the Mediterranean is covered with ooze.
The regions of the Mediterranean immediately below the surface abound in animal life, particularly on the coasts of Sicily and Southern Italy ; but nearly all species, whether fish, testacea, or others, are of Atlantic origin. The Mediterranean, in spite of its vast extent, as far as its fauna is concerned, is nothing but a gulf of the Lusitanian Ocean. Its longitudinal extension and the similarity of climate in its various portions have favoured the migration of animals through the Strait of Gibraltar as far as the coasts of Syria. At the same time, animal life is most varied near this point of entry, and the species met with in the western basin are generally of greater size than those which exist in the eastern. A very small pro-portion of non-Atlantic species recalls the fact that the Mediterranean formerly communicated with the Red Sea and the Indian Ocean. But amongst a total of more than eight hundred molluscs there are only about thirty which have reached the seas of Greece and Sicily through the ancient straits separating Africa from Asia, instead of through the Strait of Gibraltar. The diminution in the number of species in an easterly direction becomes most striking when we reach the narrow channel of the Dardanelles and the Bosphorus. The Black Sea, in fact, differs essentially from the Mediterranean proper as regards temperature. It is refrigerated by northeasterly winds sweeping over its surface, to the extent even of portions of it becoming now and then covered with a thin coating of ice, adhering to the coast. The Sea of Azof has frequently disappeared beneath a thick crust of ice, and even the whole of the Black Sea has been frozen over in winters of exceptional severity. The cold surface waters, together with those conveyed into the Black Sea by large rivers, descend to the bottom, and prove most detrimental to animal life. Echinodermata and zoophytes are not met with at all in the Blaek Sea; certain classes of molluscs, already rare in the Levantine Sea and the Archipelago, are likewise absent ; and the total number of species of molluscs is only one-tenth of what it is in the Mediterranean. Fish are numerous as far as individuals go, but their species are few. In fact, the fauna of the Black Sea appears to resemble that of the Caspian, from which it is cut off, rather than that of the Greek seas, with which the Sea of Marmara connects it.
In addition to the species which have found a second home in the Mediterranean, there are some that must still be looked upon as visitors. Such are the sharks, which extend their incursions to the seas of Sicily, to the Adriatic, and even to the coasts of Egypt and Syria. Such, also, are the larger cetacea—whales, rorquals, and sperm whales—whose visits, however, are confined now to the Tyrrhenian basin, and become less frequent from century to century. The tunny-fish of the Mediterranean are also visitors from the coasts of Lusitania. First-rate swimmers, they enter through the Strait of Gibraltar in spring, ascend the whole of the Mediterranean, make the tour of the Black Sea, and return in autumn to the Atlantic, after having accomplished a journey of some 5,600 miles. In the opinion of the fishermen the tunnies go upon their travels in three immense divisions or shoals, and it is the central shoal which visits the coasts of the Tyrrhenian Sea, and consists of the largest and strongest fish. Each of the three divisions appears to be composed of individuals about the same age. For mutual protection they swim in troops, for they are preyed upon by enemies innumerable. Dolphins and other fish of prey follow their track, but their great destroyer is man. In the summer the tunny fishery, or tonnaro, is carried on in numerous bays of Sicily, Sardinia, Naples, and of Provence. Enormous structures consisting of nets enclose these bays, and they are ingeniously arranged so as to close gradually around the captured fish, which, passing from net to net, find themselves at last in the " chamber of death," where they are massacred. Millions of pounds of flesh are annually obtained from these floating " slaughter-houses," yet the tunny appears year after year in multitudes, and on the same coasts. There may have been a slight decrease in the number, but their closely packed masses still invade the " Golden Horn " of Byzance and other bays, as they did when first they attracted the attention of Greek naturalists.
Next to the tunny fisheries those of the sardines and anchovies are most important. Sea-urchins and other products of the sea are eaten by the inhabitants of the coasts, particularly in Italy, but there is no part of the Mediterranean where animal life is so abundant and so prodigious in quantity as on the celebrated banks of Newfoundland, or on the coasts of Portugal or of the Canaries.
A large number of fishing-boats are engaged, not in the capture of fish, but in the collection of articles of dress or of the toilet. The purple-shell fisheries on the coasts of Phoenicia, the Peloponnesus, and Greece are no longer carried on, but hundreds of boats are employed annually during the fine season in fishing for coral or sponges.
Coral is found most abundantly in the western portion of the Mediterranean, and the Italian fishermen do not confine themselves to their own shores—to Sicily, Naples, and Sardinia—but also visit the Strait of Boniflcio, the sea off St. Tropez, the vicinity of Cape Creus in Spain, and the waters of Barbary. Ordinary sponges are collected in the Gulf of Gabes, and at the other extremity of the Mediterranean, on the coasts of Syria and Asia Minor, and in the straits winding between the Cyclades and Sporades. Sponges are usually found at a depth of from 12 to 150 feet, and can be gathered by divers ; whilst coral occurs at far greater depths, and has to be wrenched off with an iron instrument, which brings up its fragments, mixed with ooze, seaweeds, and the remains of marine animalculae. This industry is still in a state of barbarism : those devoted to it are not as yet sufficiently acquainted with the sea and its inhabitants to enable them to carry on the sponge and coral fisheries in a rational manner. Yet this they must aim at : they must learn how to deprive Proteus, the ever-changing deity, of his dominion over the inhabitants of the deep.
Next to the fisheries, the preparation of sea salt constitutes one of the leading industries of the Mediterranean coast-lands. But this industry, too, is frequently carried on in a primitive way, and only in the course of the present century have scientific methods been introduced in connection Iv ith it. The Mediterranean is admirably suited for the production of salt, for its waters have a high temperature, they hold a very large quantity of salt in solution, the rise and fall of the tides are inconsiderable, and flat seashores alternate with steep coasts and promontories. The most productive salt marshes of the Mediterranean are probably those on the Lagoon, or tang de Thau, near Cette, and on the littoral of Hyères; but consider-able ones may also be met with on the coasts of Spain, in Italy, in Sardinia, Sicily, Istria, and even on the " limans " of Bessarabia, bordering upon the Black Sea. The annual production of salt is estimated at more than a million tons, and exceeds, therefore, the entire tonnage of the commercial marine of France.* But this quantity, large as it is, is infinitesimal if we compare it with the saline contents of the sea, and science will enable us one day to raise a far more abundant treasure from its sterile depths.