Fisheries resources in the deep waters of the eastern Mediterranean (Greek Ionian Sea)

Abstract

The deep waters of the Greek seas are unexploited, since trawling is carried out mainly down to 400 m. In the present work, the fisheries resources of the deep waters (300-900 m) of the Greek Ionian Sea were studied in spring, summer and autumn 2000 by means of experimental trawl surveys. The results showed that in the zone 300-500 m, fish composed 73-83% by number or 89-92% by weight of the catch depending on the season, crustaceans 16-25% by number or 6% by weight and cephalopods 1-2% by number or 3-5% by weight. In the zone 500-700 m, crustaceans composed 28-41% by numbers or 67-80% by weight of the catch, whereas the proportion of cephalopods was less than 1% by number and about 1% by weight. In the deepest zone (700-900 m), the proportion of cephalopods remained negligible, whereas the proportion of fish increased and was about equal in numbers with that of crustaceans, whereas in weight it ranged from 81 to 86%. The CPUE of commercial fish was 23-59 kg/hr in the first depth stratum, 7-25 kg/hr in the second one and 2-10 kg/hr in the third one, depending on the season. Concerning the commercial crustaceans, their CPUE was 3-6.5 kg/hr in the shallowest zone, 6-8.5 kg/hr in the middle one and 2-4 kg/hr in the deepest one. The commercial part of cephalopod catch ranged from 1 to 7 kg/hr in the zone 300-500 m, whereas deeper it was negligible. Commercial/total ratio by weight of the whole catch was highest in the 500-700 m zone (0.60-0.78), whereas in the other zones it was generally lower than 0.50.