This paper considers the potential role of the crinoid Leptometra phalangium as an indicator of highly productive areas along the shelf break that can sustain large biomasses of benthopelagic fish and recruits. The structure of fish assemblages in the central Mediterranean Sea (central-western coast of Italy), analysed on the basis of surveys carried out in summer and autumn from 1997 to 2001, revealed the presence of a well-defined group of species on the shelf break. This area, occurring at a depth of between 120 and 170 m, is characterised by detritic organogenic sediments colonised by the crinoid L. phalangium, a suspension-feeding macro-epibenthic species confined in the Mediterranean to the shelf-break area. Its abundance in the studied area can reach 12-15 ind. m )2 . A total of 121 species belonging to 66 families of demersal organisms (crustacean decapods and stomatopods, cephalopods, selaceens and teleosteens) were caught at shelf-break stations from September to October. The species which typified the assemblage were the fishes Trisopterus minutus capelanus, Merluccius merluccius, Glossanodon leioglossus, Argentina sphyraena, Capros aper, Macroramphos scolopax and Lepidotrigla cavillone, the crustacean decapod Parapenaeus longirostris and the cephalopods Illex coindetii and Todaropsis eblanae. Detritic shelf-break stations showed a higher abundance of demersal organisms than stations distributed on muddy bottoms in the same depth range (100-200 m). Such differences appeared to be significant in September-October, when a clear increase in benthopelagic zooplanktivorus species, such as Glossanodon leioglossus, Trachurus trachurus, Trachurus picturatus, was found. The length structure of species occurring on the shelf break showed that for some of them the selection of this area is related to specific phases of their life cycle. Significant highest abundance of recruits and juveniles was observed for Merluccius merluccius, Helicolenus dactylopterus, Phycis blennoides, Parapenaeus longirostris and Capros aper in at least one of the two seasons. Similarly, an increased abundance of spawners of red mullet Mullus barbatus and four-spotted megrim Lepidorhombus boscii was observed on the shelf break. Results of this study may have important consequences for management of fish stocks and assemblages in the central Mediterranean. The cooccurrence of high densities of L. phalangium and benthopelagic fish, occurring mainly with juveniles and spawners, strongly indicates a potential role of L. phalangium as an indicator of highly productive areas around the shelf break. Such areas appear to play a major role in the production of some of the most abundant and commercially important fish species, such as the Mediterranean hake and red mullet.

We investigated the eVects of body size, feeding strategy and depth distribution on the trophic resource partitioning among the 26 dominant Wsh consumers in a Wsh assemblage on the central Mediterranean shelf-break. The Wsh assemblage was structured in two major trophic guilds: epibenthic and zooplanktonic feeders, according to the position of each predator along the benthos-plankton gradient. Within each main guild, the species were segregated along a prey-size or Wsh-size gradient into Wve further guilds. Fish size and prey size were strongly correlated, indicating that the prey-size niche can be well explained by predator size. Fish consumers showed a signiWcant negative correlation between the similarity in prey type and the similarity in depth distribution; most species with similar trophic preferences segregated along the depth dimension. The only predators overlapping in both food and depth preferences were those with a more specialist trophic behavior. These results suggest that Wsh body size and depth preferences are the two main niche dimensions, explaining a large part of the coexistence between the Mediterranean shelf-break Wsh consumers.Communicated by X. Irigoien.

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SUMMARY:The sexual maturation and the growth of the salema, Sarpa salpa (Linnaeus, 1758), along the Italian Mediterranean coast (central Italy), were studied in fish (n = 105) killed incidentally by underwater explosions during the construction of Civitavecchia harbour in 1999 and specimens collected with trammel nets (n = 339). This species is characterized by a protandric hermaphroditism and the sex change process occurs between 24 and 31 cm TL corresponding to a wide range of ages (3-7 years). Size at maturity (L 50 ) was 19.5 cm, at which almost all the individuals were males. Two distinct spawning periods were observed: one in spring, from March to May, and the other in autumn, from the end of September to November. During the first year, compensatory growth occurred in the individuals born in the two periods. An annual regular pattern of ring deposition was identified in the otoliths: the translucent ring was laid down during the winter months, while the opaque ring was formed during the summer months. Back-calculated lengths at age were used to estimate the parameters of the Von Bertalanffy growth equation which were: L ∞ = 37.27 cm, K = 0.27 year -1 and t 0 = -0.53 year. Salema showed isometric growth (b = 3.04; P = 0.84; t = 0.19).Keywords: reproduction, protandrous, lengths-at-age, otoliths.RESUMEN: PATRÓN REPRODUCTIVO Y CARACTERÍSTICAS DE LA POBLACIÓN DE LA SALEMA, SARPA SALPA (OSTEICHTHYES: SPARIDAE) EN EL MAR MEDITERRÁNEO. -La maduración sexual y crecimiento de Sarpa salpa (Linnaeus, 1758) en las costas del Mediterráneo italiano (Italia central) fueron estudiadas a partir de la recolecta de ejemplares muertos accidentalmente (n = 105) como consecuencia de las explosiones submarinas acaecidas durante la construcción del puerto de Civitavecchia en 1999, así como de ejemplares recolectados mediante redes de arrastre (n = 339). Esta especie se caracteriza por un hermafroditismo protándrico, ocurriendo el proceso de cambio sexual entre los 24 y 31 cm TL, los cuales corresponden a un amplio rango de edades (3-7 años). La talla de maduración (L 50 ) fue de 19,5 cm, siendo la casi la totalidad de los individuos eran de sexo masculino. Se observaron dos períodos diferentes de reproducción: uno en primavera, de marzo a mayo y otro en otoño, de finales de septiembre a noviembre. Se observó, durante el primer año, un crecimiento compensatorio ocurrido entre los individuos nacidos en los dos períodos. Se identificó en los otolitos un modelo anual y regular de deposición de anillos. Se observó el depósito de un anillo translúcido durante los meses invernales, mientras que otro opaco se formó durante los meses de verano. Las composición por edades y tallas retrocalculadas se utilizaron para estimar los parámetros de la ecuación de crecimiento de Von Bertalanffy, es decir: L ∞ = 37,27 cm, K = 0,27 año -1 y t 0 = -0,53 año. S. salpa demostró un crecimiento isométrico (b = 3,04; P = 0,84; t = 0,19).

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A total of 30 specimens (73-95 mm standard length) of Nemipterus randalli were collected along the Lebanon coast. This species, a Lessepsian migrant previously misidentified as Nemipterus japonicus, appears to be well established in the Levantine basin of the Mediterranean Sea. The small size and immature status of the specimens of N. randalli collected from the Lebanon coast indicate recent successful recruitment.

The rationale applied for monitoring and managing fisheries is based on the implicit assumption that yield and stocks status is essentially determined by fisheries. Moreover, the fisheries yield is quantified and analyzed in terms of landings with respect to official management area of registration of vessels. In this way, the real area of activity of each fleet is not considered and this prevent an effective spatial analysis of the factors affecting fisheries yield and stocks status. This paper firstly presents a VMS-based reconstruction of the fishing effort and of the area of activity of the Italian trawlers in the Mediterranean Sea. The fishing area of each fleet is then used as a spatial reference to estimate primary productivity rate and gross primary production and to investigate, by using General Additive Models, the effects of trawling effort, primary production and time on fisheries yield, fisheries productivity and overexploitation rate for some key demersal species. The results evidence that the usage of satellite-based information of fishing activities and of primary production, when combined at the real spatial scale of fishing activities, could effectively improve our ability to analyze the response of the ecosystems to these driving forces and allow capturing the main trends of yield, productivity and overexploitation rate of demersal stocks.