Diet comparison of four ray species (Raja clavata, Raja brachyura, Raja montaguiandLeucoraja naevus) caught along the Portuguese continental shelf

Abstract

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.

Feeding ecology of demersal elasmobranchs from the shelf and slope off the Balearic Sea (western Mediterranean)

“…In accordance with previous studies carried out in both the Mediterranean (Romanelli et al, 2007;Saglam and Bascinar, 2008) and the Atlantic (Ellis et al, 1996;Gomes et al, 1998;Farias et al, 2006), the dominant prey taxa in all the batoid species, except M. aquila, were natantian crustaceans and teleosts. However, the diet of M. aquila was highly specialized in anomuran crustaceans and non-cephalopod molluscs (mainly bivalves), two prey groups that, with the exception of anomurans in S. canicula, were barely present in the rest of species; M. aquila was also characterized by being the only species that did not prey on teleosts and by the moderate importance of polychaetes.…”

“…The diet of R. miraletus differed slightly from that of the other skates, as it preyed mainly on a mixture of brachyuran crabs and natantian crustaceans and displayed a narrow niche breadth. In accordance with previous studies (Farias et al, 2006;Saglam and Bascinar, 2008), the skate R. clavata based its diet on teleosts and reptantian and natantian crustaceans, showing no trend with depth.…”

Food habits of the rough rayRaja radula(Chondrichthyes: Rajidae) from the Gulf of Gabès (central Mediterranean Sea)

“…Diet shift with size is a pattern widely observed in elasmobranchs (Lucifora et al 2009). This shift can be associated with changes in morphometric characteristics, food preference with growth and swimming capacities of the species, as has been observed for other rajids (Farias et al 2006). This shift indicates an ontogenetic shift in diet potentially associated with the energetic requirements of the adults.…”

A Tale on the Demersal and Bottom Dwelling Chondrichthyes in the South of Sicily through 20 Years of Scientific Survey

“…Juvenile Cuckoo Rays feeds mainly on small crustaceans while adults also feed on polychaetes and bony fish (in Ref. [82]). Bycatch of bottom trawl fisheries (in Ref.…”

“…Excluding bony fish, polychaetes were the most common prey followed by shrimps and brachyuran crabs and cephalopods (in Ref. [82]). It is taken as bycatch in mixed demersal fisheries using trawl, gill nets and longlines elsewhere in its range (in Ref.…”