No abstract

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.

Recent data are presented on leafscale gulper shark Centrophorus squamosus and Portuguese dogfish Centroscymnus coelolepis collected during an extended sampling programme carried out at mainland Portuguese landing ports. Although there are some features common to all deepwater squaliform sharks, the two species have different reproductive strategies: C. squamosus has a lower fecundity and larger total length (L T ) at first maturity than C. coelolepis. Despite the scarcity of pregnant C. squamosus in the samples, the L T at birth was estimated at c. 440 mm. For C. coelolepis the results suggest the existence of a non-annual reproductive cycle with two breeding seasons in each year.

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.

Black scabbardfish is a deep-water species, common in the NE Atlantic at depths between 450 and 1300 m, currently exploited by some European countries. Between May 1998 and April 2000, specimens collected at three different locations in the NE Atlantic—NW of Scotland, Sesimbra (mainland Portugal) and Funchal (Madeira)—were analysed. The evolution of maturity of both sexes throughout the year was studied based on the macroscopic and microscopic analysis of the gonads. Specimens with the largest total length were found in Funchal, whereas the smallest size was recorded in the NW of Scotland. Neither spawners nor post-spawners were ever observed in NW of Scotland and Sesimbra. In Sesimbra, only a few individuals attained pre-spawning stage and most of the early developing females exhibited atresia in their ovaries. In Funchal, all the maturity stages were found; spawners occurred from September to December (females) and from August to December (males). Length of first maturity for females was estimated to be around 1000 mm. Two groups of spawners with different sizes were observed during the spawning period off Madeira.