Raja asterias population assessment in FAO GFCM GSA17 area

Abstract

Population structure and distribution of the starry ray, Raja asterias, were described based on data collected during yearly rapido trawl surveys (SoleMon), between 2005 and 2014 in the Northern and Central Adriatic Sea. A total of 306 individuals were caught, sex ratio was 1.04:1 in favor of males and length-weight relationships were obtained for the whole sample. Following the MEDITS scale, maturity was estimated, observing a higher number of immature individuals. Relative abundance significantly increased during the recent period with the highest values recorded at 5-30 m depths. Such increase could be related to the response of R. asterias to climatic change or to the decrease in fishing pressure in the area. Clear spatial segregation of individuals depending on their life stage was observed, with immature individuals inhabiting the coastal areas and adults more abundant at depths greater than 40 m. The comparison of the result of the present study with MEDITS survey outcomes in terms of distribution patterns, persistence areas of adults and juveniles and abundances indices, evidences that SoleMon survey seems to be more suitable in defining such features of the stock, likely due to the greater catchability of the rapido trawl in respect to the MEDITS trawl net. However, further investigations are needed to identify factors affecting the increasing abundance of this species, and develop an action plan for spatial management of fishing activities.

On the presence of Dipturus nidarosiensis (Storm, 1881) in the Central Mediterranean area

“…Based on the data recorded, despite the few specimens analysed, the Norwegian skate showed that a bathymetric segregation of juveniles occurred only in the upper part of the slope, and sub-adults and adults occurred at lower depths, which was previously reported in Sardinian waters (Follesa et al, 2012). This deep segregation by the ontogenic phase was also observed in other species of skates, including Raja clavata , R. asterias and Rhinoptera bonasus (Rousset, 1990; Ferrá et al., 2016; Fisher, Call & Grubbs, 2013; Ellis et al., 2005). In addition, the finding of Ionian and Adriatic D. nidarosiensis specimens on compact mud bottoms confirmed that the species prefers this type of sea bed, which was also observed by Follesa et al (2012) in Sardinian waters.…”

Batoid Abundances, Spatial Distribution, and Life History Traits in the Strait of Sicily (Central Mediterranean Sea): Bridging a Knowledge Gap through Three Decades of Survey

“…In the Mediterranean, according to the most recent assessment of the IUCN, 50% of the considered rays (16 of 32 species) are facing a high risk of extinction [ 11 ]. In addition, the lack of most basic life-history data and taxonomic uncertainties make it harder to assess their status (see, e.g., in [ 54 , 55 ]). Bradai et al [ 29 ] underlined that some neritic species have almost locally disappeared (e.g., R. alba ) or should be considered as highly depleted ( R. polystigma ), whereas few species are quite stable (e.g., R. clavata and R. miraletus ), although considered by the authors in a depleted status (i.e., quite low standing stock in weight).…”

“…The highest average individual weight (g) was reported, in decreasing order, for GSA 11 and GSA10 (Southern and Central Tyrrhenian Sea) as well as GSA19 and GSA09 (Ligurian Sea and Northern Tyrrhenian Sea). Ferrà et al [ 54 ], analyzed the data obtained from a modified beam trawl in GSA17 (the so-called “rapido” survey, i.e., Solemon) held between 2005 and 2014, and they found an increasing trend in the occurrence of this species over the years. The maximum TL was lower when compared to other Mediterranean specimens [ 79 , 96 ].…”

Strongly structured populations and reproductive habitat fragmentation increase the vulnerability of the Mediterranean starry ray Raja asterias (Elasmobranchii, Rajidae)

“…This species inhabits muddy or sandy bottoms from shallow waters to 150 m depth with age‐related abundance (Catalano et al, 2003; Romanelli et al, 2007). In particular, juvenile (total length 80–90 mm) and adult individuals appear to aggregate differently in the north and central Adriatic Sea (Serena, Mancusi & Barone, 2010; Ferrà et al, 2016). Raja asterias is an ecologically important predator within the demersal community that feeds on a wide variety of resources, including crustaceans, teleosts, and cephalopods (Capapé & Quignard, 1977; Cuoco, Mancusi & Serena, 2005; Serena et al, 2005; Romanelli et al, 2007; Bradai, Saidi & Enajjar, 2012, Coll, Navarro & Palomera, 2013; Navarro et al, 2013).…”