Objective The annual catches of demersal fish in Greek seas have remained almost constant for the last years, despite the considerable increase in the fishing effort. This is partly due to the low productivity of the Greek waters and the Mediterranean Sea in general, to the slow rate of modernization of the fleet and introduction of new fishing technology, and to the limitation of the fishing grounds suitable for demersal trawling, and partly to the shortage of scientific data upon which an effective management scheme can be based. This research aims to contribute to the knowledge on the abundance and distribution of the following demersal species: Merluccius merluccius, Mullus barbatus, Micromesistius poutassou, Trisopterus minutus capelanus, Pagellus erythrinus, Phycis blennioides, Trigla lyra, Nephrops norvegicus, Aristeus antennatus and Aristaeomorpha foliacea, which are of primary importance to the trawl fishery in the North Aegean Sea (Greece), using existing evaluation techniques. Also, to obtain information on the biology of the species concerned and to assess the factors affecting changes in the yield, abundance of the stocks and dynamic equilibrium within the ecosytem. Finally, to introduce for the first time in Greece techniques for the study of ichthyoplankton and 0-group stages of some commercially important gadoid species in order to identify spawning seasons, spawning grounds and nurseries. The results obtained would help to improve the exploitation system by suggesting measures aimed at the rationalization of the fish ries. A study of demersal stocks in the north and west Aegean Sea was carried out in 8 commercial trawler with the duration of each haul ranging between 60-120 minutes, depending on the season, the geographical location and the level of catch.The following points have been examined for each target species: seasonal abundance; geographical, seasonal and vertical distribution; length and age composition; growth, assessed by standard techniques; mortality rate (total, fishing and natural); age and season of recruitment; reproduction, sex ratio, age at maturity stages; feeding habits; location of nursery and spawning grounds; eggs and larvae distribution; eggs, larvae and 0-group distribution of hake; total biomass assessment for each target species, as well as study of the biotic parameters which could affect the distribution of the studied species.A total of 143 fish species and 29 cephalopods were identified in the study area. The ichthyofauna and teuthofauna of the area consisted mainly of Atlanto-Mediterranean taxa with some boreal and truly tropical elements. Most of the collected fish larvae were pelagic or mesopelagic. More fish eggs were generally caught in the west than in the north Aegean Sea, with reproduction of most species taking place between March and June. The concentration of fish larvae was also higher in the west Aegean Sea than in the north Aegan Sea. No clear seasonal trends in the abundance of hake larvae was established, although there is some evidence that their abundance is higher during the winter months. An analysis of the species of low or no commercial value, but exhibiting high abundance in the catches, was also provided.The biomass values were higher in the north Aegan Sea when compared with the west Aegean Sea, while biomass values exhibited substantial differences between the various depth zones, a fact corroborating the view that fish stocks undertake seasonal vertical migrations. The seasonal variations of the biomass estimates did not seem to be influenced by the period when trawlers operate, especially in the north Aegean Sea which is the largest fishing ground of the Greek seas. The seasonal and depth biomass variations are most possibly related to the biology and ecology of the fish populations.Due to the risk of damaging the fishing net, the fishermen are reluctant to operate hauls in new fishing grounds. It is therefore hoped that the results of the experimental fishing will also be of help to the fishermen to identify new fishing grounds and increase their operational area. Fields of science agricultural sciencesagriculture, forestry, and fisheriesfisheriessocial sciencessociologydemographymortalitynatural sciencesbiological sciencesecologynatural sciencesbiological scienceszoologyichthyologyagricultural sciencesagricultural biotechnologybiomass Programme(s) FP2-FAR - Community research and coordination programmes (EEC) in the fisheries sector, 1988-1992 Topic(s) Data not available Call for proposal Data not available Funding Scheme Data not available Coordinator NATIONAL CENTRE FOR MARINE RESEARCH EU contribution No data Address Aghios Kosmas Hellinikon ATHENS Greece See on map Total cost No data Participants (1) Sort alphabetically Sort by EU Contribution Expand all Collapse all Università degli Studi di Bari Italy EU contribution No data Address Via Giovanni Amendola 165/A 70126 Bari See on map Total cost No data
