Many sharks and skates are particularly vulnerable to overfishing because of their large size, slow growth, late maturity and low fecundity. In Europe dramatic population declines have taken place in common skate (Dipturus batisL.), one of the largest demersal fish in regional shelf seas, leading to extirpations from substantial parts of its former range. Here we report the discovery of cryptic species in common skate collected from the northeast Atlantic continental shelf. Data from nuclear microsatellite markers indicated two clearly distinct clades and phylogenetic analysis of mitochondrial DNA sequences demonstrated monophyly of each one of them. Capture locations showed evidence of strong spatial segregation, with one taxon occurring mainly in waters off the southern British Isles and around Rockall, while the other was restricted to more northerly shelf waters. These apparently cryptic species showed overlapping substrate and depth preferences, but distributional limits were closely related to temperature gradients, potentially indicating thermal limits to their distributions. This discovery of hidden diversity within a large, critically endangered marine vertebrate demonstrates how marine biodiversity can be underestimated, even in such a relatively well-studied and heavily exploited region.

Data on the diet of species are important for understanding ecosystem dynamics and are fundamental for the implementation of recent approaches in stock assessment and consequently for the establishment of more ecological management measures. In mainland Portugal, as in most European countries, skates and rays represent an important proportion of commercial landings. The four main species landed are Raja clavata and Raja brachyura, followed by Leucoraja naevus and Raja montagui. This paper analyses their diets based on the examination of stomach contents. Food items were identified to the lowest identifiable taxon and were further assembled into major taxonomic groups designated as prey. Intra- and interspecific comparisons were made according to size and sex. All four species had generalized diets with differences in prey preference among them. Decapods and bony fish were the most frequent prey. Furthermore, an ontogenetic dietary shift was evident in all species at around 45−55 cm total length. Both intra- and interspecific differences observed seem to be related to size and morphological characteristics of the species, as well as type of dentition. These variations allow different species, as well as small and large specimens from the same species, to exploit a larger diversity of habitats. Les données sur le régime alimentaire sont importantes pour comprendre la dynamique des écosystèmes, et sont fondamentales pour mettre en œuvre les approches récentes de gestion des stocks, et donc pour établir des mesures de gestion plus écologiques. Au Portugal, comme dans les autres pays européens, les raies représentent un part importante des débarquements commerciaux. Les quatre espèces principales débarquées sont Raja clavata et Raja brachyura, suivies de Leucoraja naevus et Raja montagui. Cet article analyse leur régime alimentaire en se basant sur les contenus stomacaux. Leurs aliments sont identifiés au taxon le plus précis possible, puis regroupés par groupes taxonomiques désignés comme proies. Les comparaisons intra- et interspécifiques des raies sont faites selon leur taille et leur sexe. Les quatre espèces présentent des différences dans leur préférence alimentaire. Les Décapodes et les poissons osseux sont les proies les plus fréquentes. De plus, un changement ontogénique est évident au niveau alimentaire, et pour les quatre espèces, autour de 45−55 cm (longueur totale). Les différences intra- et interspécifiques observées semblent liées à la taille et aux caractéristiques morphologiques de l'espèce, ainsi qu'à la dentition. Ces variations leur permettent quelle soit la taille d'exploiter une plus grande diversité d'habitats.

Elasmobranchs represent important components of marine ecosystems, but they can be vulnerable to overexploitation. This has driven investigations into the population genetic structure of large-bodied pelagic sharks, but relatively little is known of population structure in smaller demersal taxa, which are perhaps more representative of the biodiversity of the group. This study explores spatial population genetic structure of the small-spotted catshark (Scyliorhinus canicula), across European seas. The results show significant genetic differences among most of the Mediterranean sample collections, but no significant structure among Atlantic shelf areas. The data suggest the Mediterranean populations are likely to have persisted in a stable and structured environment during Pleistocene sea-level changes. Conversely, the Northeast Atlantic populations would have experienced major changes in habitat availability during glacial cycles, driving patterns of population reduction and expansion. The data also provide evidence of male-biased dispersal and female philopatry over large spatial scales, implying complex sex-determined differences in the behaviour of elasmobranchs. On the basis of this evidence, we suggest that patterns of connectivity are determined by trends of past habitat stability that provides opportunity for local adaptation in species exhibiting philopatric behaviour, implying that resilience of populations to fisheries and other stressors may differ across the range of species.

Sperm storage in males and females was studied for the deepwater shark Portuguese dogfish Centroscymnus coelolepis. In males, sperm is stored in the seminal vesicle from early maturity stages until mating. The epithelium of the seminal vesicle secretes an acid mucopolysaccharide that might preserve sperm until it is released. The oviducal gland (OG) presents the four distinct zones described for other elasmobranchs: club, papillary, baffle and terminal. Mature, pregnant, resting and regenerating females are able to store sperm in the terminal zone. Sperm was found within sperm storage tubules (SSTs), involved by a secretory matrix. The localization of SSTs deeper in the OG suggests long‐term sperm storage, which is in agreement with the long reproductive cycle described for this species. Sperm storage is an advantage for this deepwater species that presents sexual segregation and lives in a food‐constrained environment, increasing the efficiency in reproduction.

Serra-Pereira, B., Figueiredo, I., Farias, I., Moura, T., and Gordo, L. S. 2008. Description of dermal denticles from the caudal region of Raja clavata and their use for the estimation of age and growth. – ICES Journal of Marine Science, 65: 1701–1709.