Homer’s fish-infested deep becomes far less so as the Aegean undergoes a major sea change

The Aegean belongs to the fish that live in it. The question is, which fish? For over the last few years, scientists have observed not only a reduction in fish stocks, but also sweeping changes in the composition of species that swim in the Aegean. Species such as the swordfish, which arrive every year from the Atlantic in order to spawn in the eastern Mediterranean and off the shores of Cyprus, have moved to the northern Aegean while tropical fish, denizens of the oceans, have been found tangled in the nets of Mediterranean fishermen with ever-increasing frequency. Climate change So far, scientists have been unable to pinpoint the exact causes of this change in piscine migratory patterns. Marine biologists, however, reckon that it might well be due to climatic change and specifically rising temperatures, which are affecting fish all over the globe. A joint finding by three research centers participating in the large European Mediterranean International Trawl Survey and its Greek successor program (2002-2006) was that stocks of some fish, such as topes, have dropped to an alarming extent. But the abundance of other fish, such as cod in the Toronaic, Saronic and Patraic gulfs, have startled biologists. «What we have also found,» said Costas Papaconstantinou, program coordinator and head of the National Center for Marine Research (NCMR), «is that the northern Aegean has large fish stocks in contrast to the southern Aegean, which has a greater number of species in far fewer numbers.» This difference, according to the director of the Kavala Fisheries Research Institute, Argyris Kallianiotis, «is due to the nutrients in the waters of the northern Aegean, which are enriched by the waters of the Black Sea and by the rivers that run into the Thracian Sea and Thermaic Gulf.» To record fish species and arrive at an estimate of their numbers, the teams of researchers used specially modified trawlers that could net big and small species that lived at depths of 10-800 meters. The records have provided useful data on where juveniles grow – fish nurseries, as they are termed by marine biologists – spawning grounds, mortality rates and chiefly «a wide knowledge of what Greek seas contain,» said Kallianiotis, which is «what Greece didn’t have up to now but has acquired after this program of many years.» One of the biggest codfish nurseries is the Toronaic Gulf in Halkidiki, where large numbers of young cod were found. Cod spawns in deep water, in areas where trawler fishing is permitted. Scientists have already been in touch with the Panhellenic Trawler Owners Union at Nea Michaniona, south of Thessaloniki, and their attempt to restrict the fishing of young cod met with a good response, even though cod was one of the species on which the fishermen’s livelihood depends. A second nursery was located south of Thasos. Similar fish nurseries of other species have been found in other areas. Research centers are now in a position to suggest rational measures to the Agriculture Ministry’s Directorate of Fishery on specific seasons and defined marine areas. In any case, the protection of marine areas of special interest and the management of fish nurseries is one of the EU’s priorities. But the Greek fishing industry’s greatest disadvantage is the disproportionate number of fishermen in relation to the population. Professional fishermen are estimated to number 40,000, while fishing vessels (the vast majority of them small) are put at 20,000. There are also thousands of amateur fishermen.