Feeding Ecology of Thornback Ray, Raja clavata (Linnaeus 1758) in Gökçeada Island, Northern Aegean Sea, Turkey

2021 ◽  
Author(s):  
İsmail Burak DABAN ◽  
Koray CABBAR ◽  
Cahide Çiğdem YIĞIN
Keyword(s):  
Feeding Ecology ◽  
Aegean Sea ◽  
Thornback Ray ◽  
Raja Clavata ◽  
Northern Aegean Sea

scholarly journals Biology of the thornback ray (Raja clavata Linnaeus, 1758) in the North Aegean Sea

2021 ◽  
Vol 50 (2) ◽  
pp. 115-127
Author(s):  
Koray Cabbar ◽  
Cahide Çiğdem Yiğin
Keyword(s):  
Aegean Sea ◽  
Total Weight ◽  
Total Length ◽  
The North ◽  
Disc Width ◽  
Thornback Ray ◽  
Raja Clavata ◽  
North Aegean ◽  
Males And Females ◽  
North Aegean Sea

Abstract The study deals with aspects of the population dynamics in the thornback ray (Raja clavata L., 1758), one of the most abundant cartilaginous fish caught in the North Aegean Sea. Females accounted for 73.08% and males 26.92% of all individuals. Total length of females and males ranged between 50.2 and 89.9 cm (disc width: 33.4–62.0 cm), and between 43.1 cm and 82.7 cm (disc width: 30.7–64.2 cm), respectively. Relationships between total length (TL) and total weight (TW), and between disc width (DW) and total weight (TW) were described by the equations: TW = 0.0041 TL3.10 and TW = 0.0178 DW3.03, respectively. Age data derived from vertebrae readings were used to estimate growth parameters using the von Bertalanffy function: L∞ = 101.71 cm, K = 0.18 y−1, t0 = −0.07 y for males and L∞ = 106.54 cm, K = 0.16 y−1, t0 = −0.28 y for females. The maximum age was 8 years for males and females. Total length at first maturity of males and females was 70.9 cm and 81.2 cm, respectively. Based on the gonadosomatic index and gonadal macroscopic observations, it was determined that the spawning period lasted throughout the year. Stomach content analysis showed that crustaceans (53.03% IRI) and teleosts (14.70% IRI) were the most preferred prey.

scholarly journals Morphological abnormality in thornback ray Raja clavata in the Irish Sea

2021 ◽  
Author(s):  
L. J. Clarke
Keyword(s):  
Irish Sea ◽  
Beam Trawl ◽  
Morphological Abnormality ◽  
Free Swimming ◽  
Pectoral Fins ◽  
North Wales ◽  
Head Section ◽  
Thornback Ray ◽  
Raja Clavata ◽  
The Irish Sea

AbstractA free-swimming thornback ray Raja clavata specimen demonstrating significant morphological abnormality is reported, captured by beam trawl in the Irish Sea off north Wales, UK. The anterior sections of both pectoral fins were separated from the head section for a length of approximately 140 mm extending from the rostrum tip to a point posterior of the spiracles, along with abnormal morphology of the gill slits. This phenomenon has been observed elsewhere but is the first documented example of this abnormality in the eastern Irish Sea, despite widespread targeting of the species across the region by commercial and recreational fishers. Possible causes and consequences of the observed abnormality are discussed.

Genetic studies in four populations of the Northern Aegean Sea, Greece

1989 ◽  
Vol 78 (1) ◽  
pp. 89-106
Author(s):  
R. Schliwa ◽  
Angela Dannewitz ◽  
K. Gilbert ◽  
H. Walter
Keyword(s):  
Aegean Sea ◽  
Genetic Studies ◽  
Northern Aegean Sea

scholarly journals THE LIVER LIPID FATTY ACID COMPOSITION OF TWO CARTILAGINOUS FISH, THE THORNBACK RAY (Raja clavata) AND THE COMMON SMOOTH-HOUND (Mustelus mustelus)

2019 ◽  
pp. 143-153
Author(s):  
Cahide Çiğdem Yığın ◽  
Fikret Çakır ◽  
Koray Cabbar ◽  
Bayram Kızılkaya ◽  
Hasan Basri Ormancı ◽  
...  
Keyword(s):  
Fatty Acid Composition ◽  
Fatty Acid ◽  
Acid Composition ◽  
Liver Lipid ◽  
Cartilaginous Fish ◽  
Lipid Fatty Acid ◽  
Thornback Ray ◽  
Raja Clavata ◽  
The Common ◽  
Lipid Fatty Acid Composition

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

2014 ◽  
Vol 94 (7) ◽  
pp. 1509-1516 ◽  
Author(s):  
Hasna Kadri ◽  
Sondes Marouani ◽  
Mohamed Nejmeddine Bradai ◽  
Abderrahmen Bouaïn
Keyword(s):  
Feeding Strategy ◽  
Stomach Contents ◽  
Ontogenetic Changes ◽  
Central Mediterranean ◽  
Gulf Of Gabes ◽  
Gulf Of Gabès ◽  
Thornback Ray ◽  
Raja Clavata ◽  
Food And Feeding ◽  
Quantitative Analyses

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 (TL), 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.

Abundance and population structure of the blue crab Callinectes sapidus (Decapoda, Portunidae) in Thermaikos Gulf (Methoni Bay), northern Aegean Sea

Crustaceana ◽  
2018 ◽  
Vol 91 (6) ◽  
pp. 641-657 ◽  
Author(s):  
Kosmas Kevrekidis ◽  
Chryssanthi Antoniadou
Keyword(s):  
Population Structure ◽  
Blue Crab ◽  
Callinectes Sapidus ◽  
Carapace Width ◽  
Seawater Temperature ◽  
Aegean Sea ◽  
Cold Season ◽  
Mean Size ◽  
Northern Aegean Sea ◽  
Fyke Nets

Abstract The blue crab Callinectes sapidus is an alien decapod established in the Mediterranean Sea. Since 2007, increased abundance has been reported from the northern Aegean Sea sustaining local scale fishery. The present work aims to assess the abundance and population structure of C. sapidus in Thermaikos Gulf using fyke nets. Population abundance, estimated as CPUE, exhibited strong temporal variability with decreased values in the cold season; this pattern was correlated with seawater temperature. Females exhibited also spatial differences with increased abundance close to the Aliakmon estuary. In total, 543 individuals were measured for carapace width. Males prevailed in the population; however, mean size was similar between sexes. Larger individuals were caught from deeper waters and the estuarine areas, whereas mean size decreased temporally. The fyke nets used proved to be size-selective, thus preventing fisheries mortality for juveniles. However, recurrent monitoring is necessary for a sustainable management of blue crab fisheries in the gulf.

Insights into the behavioural responses of juvenile thornback ray Raja clavata to alternating and direct current magnetic fields

2021 ◽  
Author(s):  
Luana Albert ◽  
Frédéric Olivier ◽  
Aurélie Jolivet ◽  
Laurent Chauvaud ◽  
Sylvain Chauvaud
Keyword(s):  
Magnetic Fields ◽  
Direct Current ◽  
Behavioural Responses ◽  
Thornback Ray ◽  
Raja Clavata
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