Commercial sharks under scrutiny: baseline genetic distinctiveness supports structured populations of small-spotted catsharks in the Mediterranean Sea

The present study, based on microsatellite markers, describes a population genetic analysis of the small-spotted catshark Scyliorhinus canicula (Linnaeus, 1758), representing one of the most abundant and commonly caught cartilaginous fishes in the Mediterranean Sea and adjacent areas. The analyses were performed to unravel the genetic features (variability, connectivity, sex-biased dispersal) of their relative geographic populations, both at the small (around the coast of Sardinia, Western Mediterranean Sea) and at a larger spatial scale (pan-Mediterranean level and between the Atlantic Ocean and the Mediterranean Sea). Individual clustering, multivariate and variance analyses rejected the hypothesis of genetic homogeneity, with significant genetic differences between the Mediterranean and Atlantic, as well as within the Mediterranean area between the Western and Eastern basins. In details, our results seem to confirm that the Strait of Gibraltar could not represent a complete barrier to the exchange of individuals of small-spotted catshark between the Atlantic Ocean and the Mediterranean Sea. In the latter area, a complex genetic structuring for S. canicula was found. Apart from differences among the Western, Eastern and Adriatic sites, within the Western basin the small-spotted catsharks around Sardinian waters are strongly differentiated from all others (both from the eastern Tyrrhenian Sea and southernmost part of the Algerian basin) and are demographically stable. Several possible mechanisms, both biological and abiotic (e.g., migratory behavior, water fronts and oceanographic discontinuities), are discussed here to explain their peculiar characteristics. Overall, the genetic data presented, both at the local and regional level, could represent a baseline information, useful for the temporal monitoring of populations, and to assess the effects of present or future fishing/management/conservation measures

The Seascape of Demersal Fish Nursery Areas in the North Mediterranean Sea, a First Step Towards the Implementation of Spatial Planning for Trawl Fisheries

The identification of nursery grounds and other essential fish habitats of exploited stocks is a key requirement for the development of spatial conservation planning aimed at reducing the adverse impact of fishing on the exploited populations and ecosystems. The reduction in juvenile mortality is particularly relevant in the Mediterranean and is considered as one of the main prerequisites for the future sustainability of trawl fisheries. The distribution of nursery areas of 11 important commercial species of demersal fish and shellfish was analysed in the European Union Mediterranean waters using time series of bottom trawl survey data with the aim of identifying the most persistent recruitment areas. A high interspecific spatial overlap between nursery areas was mainly found along the shelf break of many different sectors of the Northern Mediterranean indicating a high potential for the implementation of conservation measures. Overlap of the nursery grounds with existing spatial fisheries management measures and trawl fisheries restricted areas was also investigated. Spatial analyses revealed considerable variation depending on species and associated habitat/depth preferences with increased protection seen in coastal nurseries and minimal protection seen for deeper nurseries (e.g. Parapenaeus longirostris 6%). This is partly attributed to existing environmental policy instruments (e.g. Habitats Directive and Mediterranean Regulation EC 1967/2006) aiming at minimising impacts on coastal priority habitats such as seagrass, coralligenous and maerl beds. The new knowledge on the distribution and persistence of demersal nurseries provided in this study can support the application of spatial conservation measures, such as the designation of no-take Marine Protected Areas in EU Mediterranean waters and their inclusion in a conservation network. The establishment of no-take zones will be consistent with the objectives of the Common Fisheries Policy applying the ecosystem approach to fisheries management and with the requirements of the Marine Strategy Framework Directive to maintain or achieve seafloor integrity and good environmental status.Versión del editor4,411

First record of Chilomycterus reticulatus (Osteichthyes: Diodontidae) in the Mediterranean Sea

The spotfin burrfish Chilomycterus reticulatus (405 mm standard length) is recorded for the first time on the shoreline of the Mediterranean Sea. The adult specimen was found dried on a beach near the south Sardinian Sea (S. Antioco's Island). Photographs and morphometrics of the specimen are give

NOTE ON HISTORICAL AND PRESENT EXPLOITATION OF CORALLIUM RUBRUM (LINNEO, 1758) IN THE CENTRAL WESTERN MEDITERRANEAN

The analyses of the landings and CPUE data from 1978 to 2005 for red coral in Sardinian seas (Central Western Mediterranean) were made. A statistical decrease in the landings can be observed. This reduction resulted very close to the decrease in the number of boats harvesting red coral. CPUE analysis at last allow to know that the average yearly amount of red coral landings by diver resulted steady with tim

Growth of a bathyal species, Alepocephalus rostratus, from the Sardinian Channel = Acrescimento di una specie batiale, Alepocephalus Rostratus, nel Canale di Sardegna

Data on age estimation and growth of Alepocephalus rostratus (Osteichthyes) (TL 9.7-45.7 cm) in the Sardinian Channel (Central-Western Mediterranean) are reported. High correlations between morphometric variables (TL, WT, OL, OW) were found. Considering the otolith rings as annual, this species was found to be very long-lived (maximum 21 yr) with a very slow growth rate

Reproductive biology of the Blonde Ray Raja brachyura (Chondrichthyes: Rajidae) in Sardinian seas = Bilogia riproduttiva di Raja brachyura (Chondrichthyes: Rajidae) nei mari sardi

The reproductive biology of Raja brachyura (Chondrichthyes: Rajidae) in Sardinian waters was analysed. A total of 839 specimens (431 males and 408 females) were collected at depth of 30-175 m in 2005-2009. Females ranged from 131 to 1055 mm in Total Length and males from 156 to 965 mm. No significant differences in size distribution among sexes were detected. Mature females and males were found during spring and summer and from winter to summer respectively. Spent specimens were found in all seasons except in autumn for females and spring for males

Validation of oviparous and viviparous ICES maturity scales through histological analysis

One of the main Tor’s of the WKSSEL2 workshop was to perform histological analyses from different structures of elasmobranchs to better confirm the validation of the macro scales per-formed in the previous WKSSEL workshop. With the intent to give a contribution to this term of reference, a description of the macroscopic and microscopic characteristics of each stage of oviparous and viviparous scales have been presented. With regard to the oviparous scales, the main features of macroscopic and histological images of the shark Galeus melastomus and the skate Dipturus oxyrinchus have been shown. Concerning the viviparous, the characteristics of two species (Etmopterus spinax and Squalus blainville) have been shown. A suggestion to amplify the description of the stage 3 (b,c,d) of viviparous scales also to the ovaries was given. This advice derives from the fact that the two species analyzed present at 3 stages a different ovaries activity: the former shows inactive gonads while the latter active ones

Deep water red coral from the island of Sardinia (north-western Mediterranean): a local example of sustainable management.

Since 1979, red coral harvesting in Sardinia has been regulated by regional laws. The regulations, including a minimum take size of 10-mm basal diameter, were imposed to limit and control harvesting. Our study indicated that.75% of the red coral colonies harvested in 2007–08 in the north-western coast were above the legal minimum size for exploitation. Moreover, extensive surveys with remotely operated vehicles allowed us to document the real structure of wild populations. Large colonies (.10 mm) represented a big portion of the population (,38% of the total), suggesting that harvesting effort did not affect yet the maximum size of colonies. All these results seem to be confirmed by the application of the model of Beverton and Holt. This model shows that the fishery of red coral in Sardinia reaches its maximum yield at an age at first capture of 20 years, an age significantly lower than the average age of 30 years calculated for the colonies actually harvested in the Sardinian coast. Our data confirmed that the measures enacted in the Sardinian regulations provide for an adequate management of this resource and, in addition, can represent a guideline for other countries that still lack a valid management plan