Diet and feeding strategy of thornback ray,Raja clavata(Chondrichthyes: Rajidae) from the Gulf of Gabes (Tunisia—Central Mediterranean Sea)

Abstract

Food and feeding strategy of the thornback ray, Raja clavata, were studied from stomach contents analysis of specimens caught monthly in the Gulf of Gabes. The data were analysed according to sex, size and season. At total of 1280 stomachs was examined, from specimens ranging from 14 to 110 cm total length (T L ), of which 1076 (83.98%) contained food. Thornback ray feed mainly on teleosts, crustaceans and cephalopods, whereas gastropods and polychaetes are occasionally consumed. Significant differences were found between the diets of males and females; however, ontogenetic changes were also detected, with crustaceans constituting the greatest proportion of the diet of smaller rays. Both teleosts and cephalopods increased in importance with growth of the skates. Prey diversity increased with size; large and mobile prey species were more commonly found in the diet of larger skates. Diet composition showed seasonal variations. Quantitative analyses and graphical methods indicate that the thornback ray is a generalist feeder.

Resource partitioning among sympatric elasmobranchs in the central-western Mediterranean continental shelf

“…However, in Sardinian waters R. asterias also preyed consistently on endobenthic items, such as Sipuncula. Raja clavata has previously been reported to display a Crustacean based (Smale and Cowley 1992;Saglam and Bascinar 2008;Valls et al 2011;Šantić et al 2012b) or piscivorous diet (Demirhan et al 2005;Kadri et al 2014a). Even if R. clavata fed mainly on Crustacea in Sardinian waters, the consumption of burrowing prey (e.g.…”

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

“…Thornback ray feeds mainly on teleosts, crustaceans and cephalopods, whereas gastropods and polychaetes are occasionally consumed (in Ref. [88]). In the Mediterranean Sea, the Thornback skate is frequently caught as bycatch in trawl fisheries targeting the Rose Shrimp (Parapenaeus longirostris) and the European Hake (Merluccius merluccius).…”

Diel vertical migration and central place foraging in benthic predators

“…Skates (Raja spp.) are widespread around the UK coast and are strongly adapted benthic mesopredators with dorso-ventrally flattened bodies, negative buoyancy, ventrally located mouths and dorsally located gill openings (spiracles) that allow the animals to respire whilst buried in sandy confirming skates to be benthophagous (Steven 1932, Ajayi 1982, Ellis et al 1996, Farias et al 2006, Šantić et al 2012, Kadri et al 2014, Pinnegar 2014. Pelagic teleosts are found in less than 2% of stomachs (Farias et al 2006, Pinnegar 2014 and are more likely to have been scavenged, being typically very abundant species such as mackerel (Scomber scombrus) or sprat (Sprattus sprattus) which occur in fishery discards.…”