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 batis L.), 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.

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.

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.

The present study focuses on age estimation, with reproductive information contributing to the better understanding of the growth and the biology of Raja undulata. In the age and growth study, two calcified structures were used: caudal thorns and central vertebra. Results of readings showed that there were no significant differences in age estimates between the two structures. Both von Bertalanffy and Gompertz growth models were fitted to size-at-age data by sex and geographical area. No significant differences were found between sexes for the two models but significant differences were found between geographical areas (P = 0.05). The Gompertz growth function was selected as the best model to describe R. undulata growth because it presented the best fit and the most reasonable biological estimates. Reproductive analysis indicates one annual breeding season for R. undulata. The differences found in the estimates of length at first maturity between geographical areas (TL50% = 838 mm in Peniche and 762 mm in Algarve for females and TL50% = 781 mm in Peniche and 736 mm in Algarve for males), together with the regional differences found between growth parameters estimates (P = 0.05), may reflect the existence of different local populations of R. undulata on the Portuguese continental shelf.

Serra‐Pereira, B., Moura, T., Griffiths, A. M., Gordo, L. S. & Figueiredo, I. (2010). Molecular barcoding of skates (Chondrichthyes: Rajidae) from the southern Northeast Atlantic. —Zoologica Scripta, 40, 76–84. Due to their vulnerability to fishing pressure, many species of skate (Rajidae) in the Northeast Atlantic are undergoing declines in abundance. The assessment of stock status and subsequent proposal of management measures are often complicated by high levels of species diversity and endemism, coupled with morphological and ecological conservatism, which makes distinguishing between species difficult. To improve the identification of skates and investigate the phylogenetic position of endemic species the cytochrome c oxidase subunit I (COI) was sequenced in 12 species (Dipturus oxyrinchus, Leucoraja naevus, Leucoraja circularis, Neoraja iberica, Raja brachyura, Raja clavata, Raja maderensis, Raja microocellata, Raja miraletus, Raja montagui, Raja undulata, Rostroraja alba) inhabiting the Portuguese waters. Based on sequence divergence R. maderensis and R. clavata only differ by 1% of the 652 bp COI sequence, questioning the recognition of R. maderensis (considered to be endemic to Madeira and the Azores), as a reproductively isolated species. Otherwise, there was clear phylogenetic support for the different genera and all the remaining species, although the genetic divergence was low compared to other chordates. In particular, COI analysis allowed clear identification of the morphologically similar species R. brachyura and R. montagui.