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The presence of non-reproductive Atlantic bluefin tuna Thunnus thynnus females in the Mediterranean Sea was investigated through histological analysis of the gonads. Three hundred and twenty-six ovary samples were collected from adults captured at different locations in the Mediterranean Sea during the reproductive seasons between 1998 and 2008. Only three specimens were considered to be in a non-reproductive state: two of them were in a reabsorbing state showing ovaries with early vitellogenic oocytes and extensive alpha and beta atresia of vitellogenic follicles; the third showed gonads with perinucleolar oocytes and was considered to be in a resting state. The low occurrence of non-reproductive individuals found in this study makes it unlikely that non-reproductive individuals aggregate with reproductive ones during their migration towards spawning grounds. Further research is suggested in order to investigate the potential presence of non-reproductive individuals on non-spawning grounds during the reproductive season.

Two trawl surveys were carried out in the summer months (June-July) of 1996 and 1997 along the whole South Adriatic area (Mediterranean sea) for the first time, using the same vessel and the same sampling gear (European Community Research Project 'MEDITS'); previous research data referred only to the south-western Adriatic side. A total list of 168 demersal species (fishes, cephalopods and crustaceans) was obtained during the surveys; species abundance data (individuals/trawling hour) were processed according to multivariate techniques in order to describe the composition and the distribution of the main species assemblages within the investigated area (10-800-m bathymetric range). Multivariate analysis of MEDITS survey catch data showed a strong relationship between fish assemblages and depth, while the influence of depth was lower with respect to cephalopod and especially crustacean assemblage distribution. © Ifremer/Cnrs/Inra/Ird/Cemagref/Elsevier, Paris

Information on distribution, relative abundance and size composition of the pleuronectiform species Citharus linguatula, Lepidorhombus boscii and Solea vulgaris was obtained during the MEDITS trawl surveys, carried out in a wide area of the Mediterranean Sea from 1994 to 1999. The three species showed a wide geographic distribution, as they were collected in all the macro-areas investigated, but with some differences in degree of presence among the 40 geographic sectors. Variations in abundance indices, analysed on a spatio-temporal basis with a Generalised Linear Model, were mostly related to the depth stratum and the macro-area. C. linguatula and S. vulgaris were especially found from 10 to 100 m depth, while L. boscii was most abundant on bottoms ranging from 100 to 500 m depth. The three species showed the highest abundance indices (kg/km2) in the Gulf of Lions, in the Greek Seas and along the Sardinian coasts. Especially for L. boscii and C. linguatula, the demographic structure showed that the sampled populations were mainly constituted by juveniles. The lowest biomass and abundance indices were obtained for S. vulgaris, whose catch was mainly composed of adult fish.