New biological data onRaja brachyura(Chondrichthyes, Rajidae) from around Asinara Island (NW Sardinia, Western Mediterranean)

Abstract

A monitoring survey on the artisanal fishery of the Asinara Island (NW Sardinia, Western Mediterranean) provided a unique opportunity to improve our biological knowledge of the blonde ray (Raja brachyura), a skate species which is rare along Mediterranean coasts. A total of 225 specimens of R. brachyura were sampled in spring 2002 and analysed in order to characterise the species in terms of reproduction, feeding habits and structure of the local population. The results enabled us to gain an insight into the ecological features of the blonde ray, including its predation on Gymnammodytes cicerellus, the Mediterranean sand-eel, a small-size fish, typical of sandy-gravel sea beds of the Mediterranean shelf.

Life-history traits of a commercial ray, Raja brachyura from the central western Mediterranean Sea

“…Similar results were found by Dorel (1986), Serra-Pereira et al (2010) and McCully et al (2012) in the Atlantic Ocean and by Catalano et al (2007) in the Mediterranean Sea for the same species (see Table 4). The same relationship was also observed in other skates from the south-west Atlantic, such as the zipper sand skate Psammobatis extenta (Garman, 1913) (Braccini & Chiaramonte, 2002, the smallnose fanskate Sympterygia bonapartii Müller & Henle, 1841 (Mabragaña et al, 2002), the shortfin sand skate Psammobatis normani McEachran, 1983(Mabragaña & Cousseau, 2004 and Bathyraja albomaculata (Ruocco et al, 2006).…”

“…This pattern has also been observed for the same species by Catalano et al (2007) along the coasts of Asinara Island (Sardinia) and Gallagher et al (2005) in the Irish waters, being a common feature among the Raijdae family (e.g. whitedotted skate Bathyraja albomaculata (Norman, 1837), Ruocco et al, 2006; thornback skate Raja clavata (L., 1758), Gallagher et al, 2005; long-nose skate Dipturus oxyrinchus (L., 1758) (Yigin & Ismen, 2010).…”

“…It is distributed in the north-east Atlantic from Norway to Morocco and is more common in the western-central than the eastern Mediterranean Sea (Ellis et al, 2005;Serena et al, 2010). Generally, it is considered an uncommon species in the Mediterranean (Matallanas, 1974;Serena, 2005), but the last observations of Follesa et al (2003Follesa et al ( , 2010, Catalano et al (2007) and Ragonese et al (2003) indicate that the Sardinian coasts and western Sicily represent a zone where R. brachyura is relatively abundant. However, the IUCN red list classified it, globally, as Near Threatened (Ellis et al, 2009) but, specifically for the Mediterranean Sea, as Data Deficient (Cavanagh & Gibson, 2007).…”

“…However, information on its general biology in the Mediterranean is very limited. Recently, only Catalano et al (2007) provided information on reproduction, population structure and feeding habits and Follesa et al (2010) on feeding, relative to the specimens caught in Sardinian seas (central-western Mediterranean).…”

Elasmobranch bycatch in a trammel net fishery in the Portuguese west coast

“…brachyura is a shallow water species (Catalano et al, 2007). In the studied area, this species appeared down to about 60 m depth with the highest catches in the higher depths.…”