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Map of central Tyrrhenian Sea showing the locality (B) where the specimen of Leucoraja circularis was caught.
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The diet of juvenile specimens of Raja radula from the Ionian Sea was investigated. The stomach contents of 43 specimens were analysed in order to evaluate composite index (IRI Index of Relative Importance). To assess feeding strategy and trophic niche width, prey-specific biomass plotted against frequency of occurrence and Levins index were used,...
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... January 2005, one specimen of Leucoraja circularis was captured by a bottom trawler operating 15 nautical miles south-east off the Anzio coast (central Tyrrhenian Sea) (Figure 1) at a depth of 500 m. The skate was taken to the laboratory and morphometric and meristic data were recorded according to Stehmann & Burkel (1984). ...
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Citations
... Σε μελέτες που είχαν γίνει στο παρελθόν σε άλλες περιοχές της Μεσογείου τα αποτελέσματα δείχνουν ότι η αναλογία του φύλου είναι κοντά στο 1:1 με ελαφρά κυριαρχία των θηλυκών(Kadri et al. 2014, Tiralongo et al. 2018.Η αναλογία φύλου των ψαριών είναι ένας σημαντικός συντελεστής για την εκτίμηση της δυναμικής του φυσικού πληθυσμού καθώς και των βιολογικών χαρακτηριστικών του είδους, όπως η μακροζωία σε σχέση με το φύλο, η ευπάθεια στα αλιευτικά εργαλεία και η χωρική κατανομή. Σύμφωνα με μελέτες που πραγματοποιήθηκαν σε άλλες περιοχές, όπως στη Τυνησία(Mejri et al. 2004) και στα ύδατα της Σικελίας(Consalvo et al. 2010), εκτιμήθηκε ότι τα αρσενικά και θηλυκά άτομα του είδους R. radula γίνονται ενήλικα (δηλαδή 100% των δειγμάτων ωριμάζουν) σε μεγέθη μεγαλύτερα από 32 cm και 34 cm, αντίστοιχα. Στην παρούσα έρευνα τα άτομα με μέγεθος μεγαλύτερο από 35 cm αντιπροσώπευαν το 66,7% του συνολικού αριθμού των αλιευόμενων ατόμων. ...
In the present study, determined morphometric characteristics were measured of Raja radula
in the North Aegean Sea from May to October 2020. Samples were collected from trammels
netsand bottom trawls. Sex ratio, disc width-total length and total length-weight relations
were estimated for both sex. Analysis was done for 309 collected specimens showed that male
juveniles are more frequently caught than females. The presence of a large percentage of
young individuals in the samples possible indicates that the study area can be considered as a
spawning area for this species. Although the present work provides a lot of new information
on this species in the northern Aegean, further study is needed.
... It is concluded that the propulsion and lift of the ray is generated by the swing of the pectoral fin through the kinematic simulation study (Yamamoto et al. 1995;Kato 2000;Xiang et al. 2014;Lu et al. 2018), and these forces and torque related to the movement of the pectoral fin are verified in the structure of the bionic ray (Udaykumar et al. 2001;Zhu and Bi 2017). At present, almost all the researches on the bionic ray mainly are focused on structural design and driving control based on the nonlinear mathematical model of the ray, as well as making underwater thrusters by using bionic ray structure (Cai et al. 2010;Consalvo et al. 2010;Liu et al. 2012;Fish et al. 2017). However, the mathematical theory of using the bionic ray structure to the ships anti-rolling has not been studied yet. ...
According to the shape and structure characteristics of ray in the ocean, a passive damping anti-rolling device was designed for fishing boats, platforms on the ocean, pontoon, heavy lift vessel and small ships that were used in maritime navigation or offshore operations. The dynamics model of the systems were established using three-dimensional (3D) computational fluid dynamics (CFD) software, the damping characteristics of the anti-rolling device was analyzed. The mathematical equation of mechanical equilibrium that satisfied the damping characteristics were deduced for the first time, and it is verified through numerical simulation analysis. The engineering feasibility and satisfactory anti-rolling effect of the device were demonstrated, and it can be seen from the experimental results that the average anti-rolling effect can reach more than 45% and more than 70% at zero speed. ARTICLE HISTORY
... This species is a relatively small skate that inhabits sandy (or mixed) and muddy bottoms, from shallow waters of 2-350 m (Mancusi et al., 2018;Tiralongo et al., 2018). Despite its conservation importance, few quantitative studies have been conducted on the feeding habits of this species (Capapé and Azouz, 1975;Abdel-Aziz, 1986;Consalvo et al., 2010;Kadri et al., 2013) and little is known about other aspects of its biology (Kadri et al., 2014), such as the sex ratio, the length-weight relationships, age and growth. ...
... Each specimen was weighed and measured (straight disc width) and the sex identified. The previous studies conducted in nearby areas, such as Tunisian (Mejri et al., 2004) and Sicilian waters (Consalvo et al., 2010), reported that males and females of R. radula become adult (i.e. 100% of the specimens become mature) above 320 and 340 mm disc width, respectively. ...
... The low percentage (3.9%) of empty stomachs (5 out of 127) of juvenile specimens of R. radula, all caught during nighttime hours, indicates that they actively feed during the night while, in the nearby area of Portopalo di Capo Passero, Consalvo et al. (2010) reported a daytime feeding habits in May-July 2005. Therefore, we can consider the juvenile of R. radula a very active feeder in the daytime and in both cold and warm months. ...
Several biological aspects of juvenile specimens of Raja radula were investigated from February to May 2017 in the central Mediterranean Sea. Diet, sex ratio, disc width-weight relationships, and size-frequency distribution were analyzed. Stomach content analysis of 127 collected specimens showed that juveniles of R. radula actively feed on small benthic crustaceans, particularly on amphipods and isopods (Idotea balthica) (%IRI values of 62.74% and 12.39%, respectively). Although the Levin's index value (Bi = 0.44) indicated that juveniles of R. radula are a moderately stenophagous feeders, active mostly on crustaceans, the analysis of the prey-specific (Pi) biomass of the main preys vs. the frequency of their occurrence (%F) showed no clear dominance. The analysis of the sex ratio showed no significant difference in sex distribution. However, there were significant differences in mean size between sexes: females were, on average, larger than males, and also the b value (slope of the curve) of the disc width-weight relationships was higher in females.
... Moreover, both species show differences in their feeding ecology, which could also be involved in the speciation process (Ingram & Shurin, 2009). While R. asterias mainly feeds on crabs and shrimps (Navarro et al., 2013), R. radula is a more generalist predator (Consalvo et al., 2010). ...
Batoidea (rays, skates and their relatives) is the largest group included in the subclass Elasmobranchii. Mediterranean Batoidea fauna is relatively diverse, characterised by a history of isolation and connectivity resulting from tectonic movements and changes in ocean circulation. The evolutionary histories of Batoidea species in the Mediterranean were estimated from two mitochondrial markers (COI and NADH2) through dating and Bayesian analyses. Additionally, two species delimitation analyses (Poisson Tree Process and General Mixed Yule Coalescent) were conducted to elucidate species boundaries. The relationship between Raja species—their ecological traits and species level phylogeny—was also studied to understand speciation in this genus. Results concerning the phylogenetic relationship between Batoidea species were largely consistent with recent molecular studies. Divergence times show a parallel evolutionary history of Batoidea fauna and Mediterranean history, which began from the Triassic. Three important speciation events were detected (a) throughout the Jurassic, when the major lineages were split (b) at the Eocene–Oligocene, when almost all genera of Batoidea were branched, and (c) during the Miocene, when almost all current species of Batoidea derived. These diversification events correspond to crucial paleoclimatic and paleogeographical events that took place at the global and local scale. Phylogenetic and species delimitation analyses revealed the presence of 18 species. Raja species showed different ecological preferences related to depth and habitat, which indicated a genus speciation process driven by different habitat characteristics.
... [30,76]). The diet of juvenile specimens of R. radula consisted mainly of crustacean decapods followed by algae, polychaetes and molluscs (in Ref. [96]). R. radula is frequently caught as bycatch in demersal trawl, gillnet, trammel net and bottom longline fisheries (in Refs. ...
... R. radula is frequently caught as bycatch in demersal trawl, gillnet, trammel net and bottom longline fisheries (in Refs. [30,96]). ...
... There is very little information on the reproductive parameters of R. radula, and no studies on the age and growth of these species in the Mediterranean Sea such as the Gulf of Tunis [9] , Gulf of Gabes [8] , Cilician Basin shelf waters (Northeastern Mediterranean) [10] , Ionian Sea [11] . This status in the Gulf of Gabes is unclear. ...
Objective: To investigate the length distribution, sex ratio, length-weight relationship, age and
growth of Raja radula in the Gulf of Gabes.
Methods: The age and growth characteristic of the rough skate (Raja radula) inhabiting in
the Gulf of Gabes (Central Mediterranean Sea) was determined. A total of 1 250 specimens were
sampled. According to the marginal increment band its growth was annual.
Results: The growth parameters were derived by using the von-Bertalanffy method and were
separately evaluated as follows: TL∞=97.2 cm, K= 0.15 y
-1
, to= 0.35, and W∞= 5.28 kg, and TL∞=
76.4 cm, K = 0.22 y
-1
, to= 0.16, and W∞= 3.77 kg, for females and males respetively. The maximum
age was 12 years for females and 10 years for males.
Conclusions: Results from this research will provide a starting point to develop a management
plan for the rough skate in the Gulf of Gabes. Further investigations are necessary to quantify the
impact of the existing regulations on the population dynamics and recruitment patterns of this
species in the region.
La presente guía incluye aquellas especies de elasmobranquios que han sido documentadas en los ambientes marinos del litoral de la Región de Murcia. Se han identificado un total de 31 especies de tiburones y rayas.
Cada una de ellas está descrita en una ficha que incluye diversos
apartados como morfología, hábitat biología y comportamiento,
presiones y amenazas, estatus y curiosidades. Además, por primera vez, se presenta un mapa actualizado de la distribución de cada especie en base a los datos obtenidos en todas las fuentes de información disponibles en el momento de la elaboración del documento.
El objetivo de esta guía es que se convierta en un recurso divulgativo
para ser utilizada como manual de campo por aquellas personas
interesadas en ampliar su conocimiento sobre estos animales
imprescindibles en el desarrollo de la vida marina y que son grandes
desconocidos para gran parte de la ciudadanía. Se trata de la primera guía disponible sobre tiburones y rayas presentes en la Región de Murcia y pretende servir de referencia para otras publicaciones de ámbito regional, estatal e internacional.
Chondrichthyes are a group of cartilaginous fish, where we have sharks, rays, and chimeras as members. This group plays an important role in aquatic ecology, as they act as predators throughout the food chain (e.g., sharks). However, many populations of Chondrichthyes are threatened by several factors (increased direct fishing, high mortality rate as accompanying fauna, marine pollution, habitat destruction, etc.). These declines are evident in many parts of the world and have come to the attention of scientists, conservation organizations, the media, and the general public. Fisheries legislation regulating international fisheries markets has been amended to provide greater protection for this group along with other species of fish. However, little is known about these species, which reinforces the importance of studies in order to have a better understanding of the elasmobranch stocks, as well as to identify the influences of the anthropic action of fishing. In response to knowledge on the low sustainability of cartilaginous fish fisheries on a global scale, FAO has developed an international plan of action for the management and conservation of these fish, with the aim of developing and implementing national plans of action to ensure management and conservation of these stocks, having as main recommendation the collection of information about the Chondrichthyes, especially the sharks. Even so, this group is little known in terms of biodiversity, ecology, behavior, and a host of other characteristics relevant to this taxon, which is very worrying. Chondrichthyes - Multidisciplinary Approach attempts to portray to the readers up-to-date information on Chondrichthyes to promote an overview of the current taxon, serving as an indispensable source of access to more accurate and detailed information on shark rays and chimeras.
The study of trophic ecology of marine predators is crucial to better understand the ecological factors that condition their role within marine ecosystems. Here we investigated the trophic habits and position of a Mediterranean endemic predator, the starry ray, Raja asterias. Specifically, we quantified the diet composition of this endemic ray in a highly exploited area of the NW Mediterranean, and we evaluated the effects of sex, maturity-stage and season on its feeding habits. Our results revealed that the starry ray is a predator of crustaceans (crabs and shrimps), and to a lower extent on teleosts, molluscs and polychaetes. This species has a high trophic position within its food web and feeds mainly on crabs (mainly Liocarcinus depurator and Goneplax rhomboides), independent of their sex, maturity-stage or season. The great importance of crabs in the diet of starry ray may be due to the fact that crabs are the dominant crustaceans in terms of biomass and abundance in the area where starry rays were collected, thus allowing them to exploit the most abundant food resource. Since the starry ray has shown a progressive decline on the catch, further research is needed to analyse the main drivers of starry ray dynamics in the Western Mediterranean Sea. Our results present important new data that will allow us to further explore the population dynamics of starry rays and the role of crustacean availability and fishing activity.
