T. Romeo

Differences among fish assemblages associated with a nearshore vermetid reef and two other rocky habitats along the shores of Cape Milazzo (northern Sicily, central Mediterranean Sea)

Fish assemblages associated with shallow rocky bottoms along the coast of Cape Milazzo were investigated within three selected habitats, each represented by a different degree of complexity and namely vermetid reef (VR), rocky-algal reef (RR) and boulder and pebbles (BP). The area, located along the northern coast of Sicily (southern Tyrrhenian Sea) was studied by using a non-destructive diver visual census methodology evaluating species composition and abundance. A total of 39 fish taxa belonging to 15 families were recorded over the three habitats investigated. Multivariate and univariate approaches detected significant differences among the three habitats. These differences were either in fish assemblage structure, in the assemblage parameters or in the abundances of some common species. A multidimensional scaling performed on the entire fish density data set showed distinct groupings for the three habitats. The highest values of mean species richness (S), diversity (H′), evenness (J) and density (N) occurred over the more complex habitat, represented by VR, than over rocky-algal reef habitat or BP. Different habitat preferences were evidenced for several fish species. Diplodus sargus , Serranus scriba , Tripterygion tripteronotus , T. delaisi and T. melanurus were significantly more abundant over VR whereas Thalassoma pavo and Symphodus tinca were more abundant both over VR and BP habitats. Statistical comparison did not detect habitat preferences in Symphodus roissali , Oblada melanura , Diplodus vulgaris and Sarpa salpa . As far as the size is concerned, small, medium and large-sized specimens of D. sargus and only large-sized individuals of D. vulgaris were significantly more abundant over the VR habitat side than over the other two. These results suggest that differences in assemblage parameters are related to habitat structure. Greater habitat complexity means greater surface available, thus providing additional resources for adults and juveniles of many species: food, cavities, caves and then new niches, refuges from predation, from artisan fishery nets, as well as resting or mating sites, boosting the total number of individuals and species. The results of this study highlight the importance of VR in sustaining the biodiversity of fish assemblages and emphasize the need for their careful management in an area already proposed as a Site of Community Interest.

Swordfish ( Xiphias gladius , Teleostea: Xiphiidae) surface behaviour during reproductive period in the central Mediterranean Sea (southern Tyrrhenian Sea)

Swordfish in the Mediterranean Sea have been caught with harpoon since 1000 BC, when, from May to August, these animals come to the surface often in male–female pairs. At this time, swordfish exhibit a variety of swimming behaviours largely only known by fishermen targeting swordfish. Over four years from 2002 to 2005, we observed the behaviour of swordfish in surface waters from the sighting platform of a harpoon fishing boat. The behaviour of 207 swordfish pairs, 73 single females and 124 single males, were recorded. On the basis of behaviours identified by the fishing fleet, we classified a priori , the behaviour of single males, single females and pairs of swordfish across seven categories. After capture, the maturity stage of each fish was determined macrocospically and assigned to a gonadosomatic index (GSI). Both male and female of a higher GSI were more frequently observed in surface waters during June and July (analysis of variance (ANOVA) F (3,276) xa0=xa070.107; P xa0=xa00.001) and individual GSI was observed to be associated with differing behavioural grouping. The most frequent behaviours observed were: a female that swam rectilinear closely followed by the male, or two fish that swam near the surface and turn out going full circle. Both behaviours were associated with the maturity Stage IV. Our data suggest that reproductive behaviour of swordfish involve a long lasting surface courtship display with different phases influenced by gonad development.

Marine litter in an EBSA (Ecologically or Biologically Significant Area) of the central Mediterranean Sea: Abundance, composition, impact on benthic species and basis for monitoring entanglement

Marine litter is commonly observed everywhere in the ocean. In this study, we analyzed 17u202fkm of video footage, collected by a Remotely Operated Vehicle (ROV) at depths ranging between 20 and 220u202fm, during 19 transects performed on the rocky banks of the Straits of Sicily. Recently, the Contracting Parties of the Convention on Biological Diversity (CBD) recognized this site as an Ecologically or Biologically Significant Area (EBSA). The research aim was to quantify the abundance of marine litter and its impact on benthic fauna. Litter density ranged from 0 items/100u202fm2 to 14.02 items/100u202fm2 with a mean (±standard error) of 2.13 (±0.84) items/100u202fm2. The observed average density was higher (5.2 items/100u202fm2) at depths >100u202fm than at shallower depths (<100u202fm, 0.71 items/100u202fm2). Lost or abandoned fishing lines contributed to 98.07% of the overall litter density, then representing the dominant source of marine debris. Litter interactions with fauna were frequently observed, with 30% of litter causing entanglement/coverage and 15% causing damage to sessile fauna. A total of 16 species showed interaction (entanglement/coverage or damage) with litter items and 12 of these are species of conservation concern according to international directives and agreements (CITES, Berne Convention, Habitat Directive, SPA/BD Protocol, IUCN Red List); we also observed 7 priority habitats of the SPA/BD Protocol. This research will support the implementation of monitoring Harm as recommended by the UN Environment/MAP Regional Plan on Marine Litter Management in the Mediterranean, and the Marine Strategy Framework Directive (MSFD). The institution of a SPAMI in the investigated area could represent a good management action for the protection of this hotspot of biodiversity and to achieve a Good Environmental Status (GES) for the marine environment by 2020, under the MSFD.

Age, growth, biological and ecological aspects of Remora osteochir (Echeneidae) in the Mediterranean Sea

This paper provides for the first time data on age and growth of Remora osteochir , also describing its sagittal otolith together with other biological and ecological aspects. Overall, 236 individuals of marlin sucker were collected in the southern-central Mediterranean Sea, from 2008 to 2009. All samples were hosted by the Mediterranean spearfish, Tetrapturus belone , caught by surface longline and harpoon. Analysis of gonads identified a reproductive peak during June and July. The estimated growth parameters according to the von Bertalanffy equation were: L ∞ = 27.37 cm TL, k = 0.248 year −1 , t 0 = −1.36 year. The length-weight relationship, computed by using eviscerate weight, highlighted an isometric growth for both sexes, as supported by the other results: similar sizes, growth curves and disc length-total length relationship.