Raja Clavata Research Articles

The Effect of Azide, Fluoride, Orthovanadate and EDTA Sodium Salts on Ecto-ATPase Activity in Erythrocytes of a Scorpionfish (Scorpaena porcus L.) and Thornback Ray (Raja clavata L.)

The Effect of Azide, Fluoride, Orthovanadate and EDTA Sodium Salts on Ecto-ATPase Activity in Erythrocytes of a Scorpionfish (Scorpaena porcus L.) and Thornback Ray (Raja clavata L.)

Using acoustically visible gillnets to reduce bycatch of a small cetacean: first pilot trials in a commercial fishery

Bycatch of protected species, particularly small cetaceans, in gillnets is a worldwide concern. One hypothesis for this is that echolocating cetaceans entangle because they do not perceive conventional gillnets as impenetrable barriers, owing to the gillnet’s faint echo. A gillnet modified for improved acoustical visibility was tested in a first pilot trial in a commercial gillnet fishery targeting turbot (Scophthalmus maeoticus) on the Turkish Black Sea coast. This study is the first demonstration of the viability of using a gillnet equipped with small acrylic glass spheres to reduce bycatch of harbor porpoises in a commercial fishery and provides the basis for full-scale sea trials of the gear in commercial fisheries through a power analysis. In these pilot experiments, the focus lied on the handling of the gear and identification of requirements for a full-scale trial, but results include promising bycatch data for an endangered echolocating marine mammal (Phocoena phocoena) and no reduction in catch efficiency of a bottom-dwelling, vulnerable species (Raja clavata).

Biological Knowledge of Thornback Ray (Raja clavata) from the Azores: Improving Scientific Information for the Effectiveness of Species-Specific Management Measures

Simple SummarySharks, rays, and skates are increasingly being recognized as endangered due to their life-history characteristics, fishing pressure, and habitat degradation. The thornback ray Raja clavata is one of the most commercially important skates in the seas of Northwest Europe. However, due to a lack of biological knowledge about this species in Azorean waters, the types of stock evaluations that can be performed are restricted. This study expands current knowledge on vertical distribution, size-frequency distributions, growth patterns, sex ratios, mortality rates, and reproduction of this species, and provides a baseline for further fishing monitoring.Elasmobranchs are globally recognized as vulnerable due to their life-history characteristics, fishing pressure, and habitat degradation. Among the skates and rays caught by commercial fisheries, the thornback ray Raja clavata is one of the most economically important in Northwest European seas. However, the scarcity of biological knowledge about this species in Azorean waters has limited the stock assessment types that can be conducted. To improve information on its habitat preferences, spatial distribution and movement pattern, growth, sex ratio, mortality, and reproduction, as well as to investigate long-term changes in abundance and size, this study analyzed approximately 25 years of fishery-dependent and independent data from the Azores. Raja clavata was mainly caught at depths up to 250 m. Most of the tagged fish were recaptured near the release point. A larger–deeper trend was found, and females were larger and more abundant than males. Life-history parameters showed that R. clavata has a long lifespan, large size, slow growth, and low natural mortality. The sustainability of its population is of concern to fisheries management and, while our findings suggested a relatively healthy stock in the Azores, a thorough increase in data quality is required to better understand the stock condition and prevent overexploitation.

Analysis of Demersal Fish Fauna off the Sea of Marmara, Turkey

Demersal fish fauna of the Sea of Marmara, Turkey was determined by bottom trawl surveys between March 2017-December 2018 at 34 stations with the monthly samplings. During the study, a total of 61 teleost and 12 cartilaginous fish species belonging to 42 families were sampled. The target, bycatch and discard rates of CPUE were determined as 13.40%, 69.64% and 16.95%, respectively. In total, 53.9% of the CPUE was stemmed from Trachurus trachurus. Mustelus mustelus, Raja clavata, Merluccius merluccius and Merlangius merlangius had the highest CPUE with a mean of 77.63, 71.86, 71.72 and 72.68 kg/km2, respectively. The highest biodiversity was observed in the southwestern part of the Marmara Sea. With increasing depth, the species number of the teleost fish decreased, whereas the species number of the cartilaginous fish increased. The mean CPUE values of the economical demersal fish species were lower in comparison to those reported from other regions in Turkey. Evidence suggests fish stocks with shallower distribution is under heavier threat against fishing pressure. Since commercial trawling is banned in the Sea of Marmara, beam trawl fishery can be considered as the major threat to demersal fish stocks in the region.

Evidence of difference in landings and discards patterns in the English Channel and North Sea Rajidae complex fishery

Bycatch species such as skates and rays are for most of them not subject to analytical stock assessment. However, their life history characteristics increased their vulnerability to fisheries. In the English Channel and North Sea area, the three main landed Rajidae species are Raja clavata, Raja brachyura and Raja montagui. The current management measure is a global TAC, common for all Rajidae species. Data to process analytical stock assessment are not available for these species, particularly discards data. A Bayesian multispecies biomass production model, following separately the landings and discards was applied to these stocks. This model provided proxies of reference points (MSY and BMSY) per species. All stocks were depleted in 1990 and are now rebuilding. However, rebuilding speeds are different within the complex, R. clavata being the fastest and R. brachyura the slowest. Furthermore, the proportion of the discards and landings to biomass differ between species, highlighting species specific fishing strategies. Differences in vulnerabilities within the Rajidae complex might be caused by the variability of life history parameters between species as well as landings and discards pattern differences. This second factor, usually not considered for data limited stock assessment, is particularly relevant for highly discarded chondrichthyans species, and might be considered when choosing new methodology to asses Rajidae stocks.

Biology of the thornback ray (Raja clavataLinnaeus, 1758) in the North Aegean Sea

AbstractThe study deals with aspects of the population dynamics in the thornback ray (Raja clavataL., 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 TL3.10and 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.

In the quest of the optimal chondrichthyan for the development of collagen sponges for articular cartilage

The limited capability of articular cartilage to self-repair renders its regeneration a formidable challenge. In the quest of the optimal material for cartilage scaffold fabrication, the use of collagen type II has been advocated, but its optimal source still remains elusive. Herein, the potential of four [lesser spotted dogfish ( Scyliorhinus canicula ), thorn back ray ( Raja clavata ), cuckoo ray ( Leucoraja naevus ) and blonde ray ( Raja brachyuran )] cartilaginous fish (chondrichthyes) derived collagen type II preparation in cartilage engineering was assessed. Collagen type II was extracted using the acid-pepsin method, crosslinked with 4-arm poly (ethylene glycol) succinimidyl glutarate sponges were fabricated and their biophysical, biochemical and biological properties were assessed. Pure collagen type II preparations were obtained from all four chondrichthyes, as revealed by gel electrophoresis. Pore size, porosity, mechanical properties, denaturation temperature, free amine content and resistance to enzymatic degradation of the produced sponges were not significantly ( p > 0.05) affected as a function of species. Biological analysis using human adipose derived stem cells revealed no significant ( p > 0.05) differences between the groups in cell viability, DNA concentration, metabolic activity, Alcian blue staining and sulphated glycosaminoglycans synthesis. Human adipose derived stem cells seeded on fish-derived scaffolds expressed lower mRNA levels of COL1A1 (fold change ≥ 2.0) and COL3A1 (apart from lesser spotted dogfish; fold change < 2.0) and higher mRNA levels of COL10A1 (fold change ≥ 2.0), COMP (fold change ≥ 2.0), SOX9 (fold change ≥ 2.0), and ACAN (apart from cuckoo ray; fold change < 2.0) than cells grown on tissue culture plastic. Our data suggest that chondrichthyes derived collagen type II has the potential to be used in cartilage engineering. • High purity collagen type II can be extracted from chondrichthyes. • Chondrichthyan extracted collagen type II scaffolds support cell growth. • Chondrichthyan extracted collagen type II scaffolds can be used in cartilage engineering.

Combination effect of hot smoking and vacuum packaging on quality parameters of refrigerated thornback ray (Raja clavata Linnaeus, 1758)

In this study, hot smoking process was applied to thornback ray (Raja clavata), which is a non-target catch, and the product obtained was vacuum packaged and then stored at refrigerated conditions (4±1 °C) for 120 days. The nutritional, chemical, microbiological, and sensory changes in the products were examined every 15 days. After the hot smoking process applied to thornback rays, significant changes were observed in the nutritional composition of the products (P&amp;lt;0.05). Total volatile basic nitrogen (TVB-N), trimethylamine nitrogen (TMA-N), and thiobarbituric acid (TBA) values of smoked thornback rays increased during storage, and these values were determined between 23.11-98.06 mg/100 g, 2.48-7.33 mg/100 g, and 0.1-0.3 mg malondialdehyde/kg, respectively. It was determined that the total aerobic mesophilic bacteria (TAMB) count detected in the fresh sample decreased in smoked products due to the smoking process and the value was found below the detectable limit value (1.47 log CFU/g) during storage. As a result of the sensory evaluation, it was determined that the texture, odor, and flavor criteria of the smoked thornback rays were below the consumable limit value on the 120th day. According to the results, it was determined that the thornback ray vacuum packaged by hot smoking can be consumed safely for 105 days at 4±1 °C. This study shows that discarded thornback rays, which are a high protein food, can be transformed into high value-added products by applying different processing methods such as smoking and so can be evaluated as human food.

Observations on Bycatch Rate for Vulnerable Fish Species on the Romanian Coast

"Living marine resources obviously contribute to the survival of humanity. Unfortunately, numerous studies highlighted that marine biological diversity faces various threats related to overfishing and illegal fishing, pollution (marine and terrestrial), invasive species, marine litter and climate change. In this context, the incidental catch of vulnerable species (i.e., elasmobranchs, marine mammals, seabirds) is considered one of the main threats to good environmental condition of the marine fauna.The aim of the study conducted in 2020, was to highlight the impact of fishing activities on aquatic resources, especially on vulnerable fish species as picked dogfish Squalus acanthias), thornback ray (Raja clavata) and common stingray (Dasyatis pastinaca), marine mammals and seabirds. The background information was collected by observations from scientific trawl surveys by pelagic and demersal trawl gears, observations from stationary fishing points, observations from commercial beam-trawl fishing operations. The analysis of logbooks of several economic operators and data collected by observers on board vessels, highlighted the low bycatch rate for vulnerable species in most fishing gear. Key Words: vulnerable species, by-catch, fishing gear "

Structure and Diversity of the Demersal Fish Assemblages off Psara Island (Central Aegean Sea) Caught by Experimental Bottom Trawling

Data with high spatial resolution on the structure and diversity of marine assemblages are valuable for fisheries management and conservation planning but are seldom available. This study provides fisheries-independent, baseline information on the structure and diversity of the demersal fish assemblages of the continental shelf and upper slope off the island of Psara (Central Aegean Sea). Experimental bottom trawl hauls were conducted during 2009–2010, using identically designed trawls. All the fish in the catches were identified onboard, enumerated, and weighted to the nearest g. Species abundance and biomass were transformed to CPUE. Forty-seven taxa were identified in the catches. For 18 of the species caught no other fisheries-independent information on their abundances and distributions is available for the wider area. Among the Elasmobranchii species collected, Squalus acanthias, Dipturus oxyrinchus, and Raja clavata are species of conservation concern. Species composition was generally more similar to that reported for assemblages of the Cretan Sea and the South Aegean Sea than for assemblages of the North Aegean. The assemblages were structured with depth, a pattern that may be driven in part by the differences in benthic habitat between depth zones. No trends by depth in total numerical abundance and species diversity were identified, whereas the bathymetric change in taxonomic diversity was attributed to the depth distributions of certain species-rich orders and families. The frequency distribution of the trophic level of the species followed the broad-scale pattern that applies in the Mediterranean Sea.

ВЛИЯНИЕ СОЛЕЙ АЗИДА, ФТОРИДА, ОРТОВАНАДАТА И ЭДТА НАТРИЯ НА ЭКТО-АТФАЗНУЮ АКТИВНОСТЬ ЭРИТРОЦИТОВ СКОРПЕНЫ (SCORPAENA PORCUS L .) И МОРСКОЙ ЛИСИЦЫ (RAJA CLAVATA L .)

The effect of azide, fluoride, orthovanadate and EDTA sodium salts on the ecto-ATPase activity in red blood cells (RBCs) of a scorpionfish (Scorpaena porcus L.) and thornback ray (Raja clavata L.) was studied. It was shown that under the influence of millimolar (mM) concentrations of the selected biochemical agents, significant differences in the hydrolytic activity of RBC plasma membrane ecto-ATPases were revealed in cartilaginous vs. teleost fish. For example, thronback ray RBC ecto-ATPase was practically insensitive to sodium azide. In contrast, scorpionfish RBC ecto-ATPase was sensitive to sodium azide, which blocked the enzyme activity by 65% at a concentration of 20 mM. Thornback ray RBC ecto-ATPase retained a significant activity (37%) at high (60 mM) concentrations of sodium fluoride, while scorpionfish RBC ecto-ATPase was almost completely blocked at this concentration. EDTA acted as a modifier of thornback ray ecto-ATPase activity: at concentrations of up to 6 mM, ATP hydrolysis was actively blocked (by 58%), and at higher concentrations, ecto-ATPase activity was stimulated (up to 20%). An increase in the EDTA concentration (up to 12 mM) in suspensions of scorpionfish RBCs constantly stimulated the inhibitory effect of the chelator (up to 52% vs. control). The activity of ecto-ATPases in RBCs of the studied fish species was weakly blocked by sodium orthovanadate. These differences may reflect a higher tolerance of thornback ray RBC ecto-ATPase to the effect of the above chemical reagents compared to a scorpionfish. The absence of the sodium azide inhibitory effect on thornback ray RBC ecto-ATPase suggests that this ecto-ATPase may be referred to a family of type 2 ecto-NTPDases (ENTPD2), while scorpionfish ecto-ATPase may belong to type 1 ecto-NTPDases (ENTPD1).

Bio-mineralization in Skeletons of Some Elasmobranches From Susah and Dernah Coasts, Libya (Estimation Study Using Nano-Technique)

Skeletons of five elasmobranches specimens: [Galeorhinus galeus, Squalus acanthias, Rhinobatus rhinobatus, Raja clavata, and Taeniura grabata] were collected from Susah and Dernah coasts between March and April 2019, and scanned by XRF with Bruker S2 Ranger 2008, to study the bio-mineralization in their skeletons. Calcium carbonates CaCO3 ranged from 46.53% in Tope Shark to 50.69% in Dogfish. G. galeus peaked at its CaO (71.11%), compared to the nadir value of T. grabata (69.03%), the same species had a significant value of SO3 (16.2%), which dropped to 9.21% in R. clavata, which had the same number as the zenith of Phosphates (P2O5), that was lower than 8% in G. galeus, as lower as Silicates (SiO2) (7.80%). Also, R. clavata had maximized values of Magnesium, Aluminum, Iron, and Manganese oxide in this work till 0.32, 0.26, 0.42, and 0.89%, respectively. Tope sharks had the lowest sum of minerals 37.39%, insignificantly as much as the sum of the mineral in Dogfish’s skeleton (39.95%). Also, S. acanthias recorded a significant Ca/P ratio (9.53:1.00), compare to R. clavata (7.70:1.00). These analyses are useful to understand and following the physiology of bio-mineralization and bio-accumulation of minerals in marine organisms in Libyan coast.

Growth and Age Validation of the Thornback Ray (Raja clavata Linnaeus, 1758) in the South Adriatic Sea (Central Mediterranean)

Raja clavata is the most widespread and landed skate species in the Mediterranean Basin. Despite its diffusion and economic importance, several aspects of its life history, such as age and growth, are poorly understood. This study evaluated the species’ growth in the South Adriatic Sea (Central Mediterranean Sea) and for the first time attempted an age validation through a tagging experiment. Thin sectioning of vertebral centra proved to be a more accurate preparation method in terms of age estimation precision and reproducibility than whole vertebral centrum staining (cobalt nitrate and ammonium sulfide technique). Marginal analysis showed a clear seasonal pattern, confirming the hypothesis of a single annulus deposition per year. A total of 291 vertebral centra were sampled and used for age estimation purposes. The oldest female was estimated to be 12 years old [total length (TL) = 89 cm], while the oldest male was aged 8 years (TL = 79.9 cm). Females were also found to be characterized by a slightly wider longevity range (ωL = 11.5, ωU = 16.8 years) than males (ωL = 7.8, ωU = 11.2 years). The von Bertalanffy growth curve fit the age and length data more accurately than the Gompertz and logistic models. Eighty-three thornback rays were tagged and released, of which two were recaptured. In both recaptured specimens, oxytetracycline marks were clearly visible. The band deposition after oxytetracycline injection and growth during the freedom period (about 1 year) were consistent with the age estimation method and criteria used and with the obtained growth results. Thus, the analysis of the vertebral centra extracted from the two recaptured specimens confirmed the hypothesis of the deposition of a single annulus per year and in general the age estimation criteria used in this study.

Karadeniz’de Vatoz Balığının, Raja clavata (Linnaeus, 1758) (Elasmobranchii: Rajidae) Üreme Zamanı ve Cinsi Olgunluk Boyu

To describe the spawning period, size at maturity (Lm), reproductive load (Lm/Lmax), length at maximum yield per recruit (Lopt) of thornback ray (Raja clavata); and to assess the differences in these parameters from other populations, a total of 18 months samplings were conducted between February 2011 and December 2013 in the southeast Black Sea. A total of 265 (160 females and 105 males) specimens of thornback ray were examined. The mean total length (L) of females was significantly greater than the mean total length of males (p&amp;lt;0.05). The GSI analysis revealed that thornback ray showed reproductive activities throughout the year. The Lm was estimated as 75.44 cm for females and 71.71 cm for males. The Lopt was estimated from the empirical relationships between the Lopt and Lm, and it was larger than Lm for both sexes.

Development and regeneration of the crushing dentition in skates (Rajidae)

Sharks and rays (elasmobranchs) have the remarkable capacity to continuously regenerate their teeth. The polyphyodont system is considered the ancestral condition of the gnathostome dentition. Despite this shared regenerative ability, sharks and rays exhibit dramatic interspecific variation in their tooth morphology. Ray (batoidea) teeth typically constitute crushing pads of flattened teeth, whereas shark teeth are pointed, multi-cuspid units. Although recent research has addressed the molecular development of the shark dentition, little is known about that of the ray. Furthermore, how dental diversity within the elasmobranch lineage is achieved remains unknown. Here, we examine dental development and regeneration in two Batoid species: the thornback skate (Raja clavata) and the little skate (Leucoraja erinacea). Using in situ hybridization and immunohistochemistry, we examine the expression of a core gnathostome dental gene set during early development of the skate dentition and compare it to development in the shark. Elasmobranch tooth development is highly conserved, with sox2 likely playing an important role in the initiation and regeneration of teeth. Alterations to conserved genes expressed in an enamel knot-like signalling centre may explain the morphological diversity of elasmobranch teeth, thereby enabling sharks and rays to occupy diverse dietary and ecological niches.

Methods for identifying and interpreting sex-linked SNP markers and carrying out sex assignment: application to thornback ray (Raja clavata).

Sex-determining modes remain unknown in numerous species, notably in fishes, in which a variety of modalities have been reported. Additionally, noninvasive individual sexing is problematic for species without external sex attributes or for early life stages, requiring cytogenetic or molecular analyses when sex chromosomes or sex-linked markers have been characterized. Genomics now provide a means to achieve this. Here, we review common sex-determination systems and corresponding statistical methods for identifying sex-linked genetic markers and their use for sex assignment, focusing on single nucleotide polymorphism (SNP) markers derived from reduced representation sequencing methods. We demonstrate the dependence of expected sex assignment error on the number of sex-linked SNPs and minor allele frequency. The application of three methods was made here: (a) identification of heterozygote excess in one sex, (b) FST outlier analysis between the two sexes and (c) neuronal net modelling. These methods were applied to a large SNP data set (4604 SNPs) for 1680 thornback rays (Raja clavata). Using method (a), nineteen putative sex-linked SNPs were identified. Comparison with the reference genome of a related species (Amblyraja radiata) indicated that all 19 SNPs are probably located on the same chromosome. These results suggest that thornback ray has a XX/XY sex-determination system. Method (b) identified eight SNPs probably located on different chromosomes. Method (a) led to the lowest sex assignment error among the three methods (4.2% error for females and 3.7% for males).

Coupling Gastro-Intestinal Tract Analysis With an Airborne Contamination Control Method to Estimate Litter Ingestion in Demersal Elasmobranchs

This study aims to assess the litter ingestion in some demersal elasmobranchs, combining a classical gastro-intestinal tract (GIT) analysis with a procedure methodology to reduce airborne fibres contamination. In order to prevent the overestimation of litter ingestion, we applied severe mitigation measures to avoid airborne contamination during the analyses, integrating a new approach for the correction of estimates of fibres abundance using control procedure. In this study, we assessed the anthropogenic litter ingestion in four elasmobranch species from the southern Tyrrhenian Sea: Scyliorhinus canicula (n= 27), Etmopterus spinax (n= 16), Galeus melastomus (n= 12) and Raja clavata (n= 6). The gastro-intestinal tract of each specimen was analysed by visual sorting and the polymers identified by FT-IR spectroscopy technique. Overall, 19 litter particles were found in the gastro-intestinal tract of 13 demersal elasmobranchs (%O= 21) and for the first time, evidence of litter ingestion by R. clavata in Mediterranean waters was also reported. In G. melastomus and R. clavata all anthropogenic particles were plastics, whereas in S. canicula other litter categories were also found. No litter ingestion was instead observed in E. spinax. More than 50% of litter particles belonged to microlitter category (< 5 mm). Polyamide was the only polymer typology found in all examined species. We described the procedures to control the airborne contamination applied at each step of laboratory analysis and, thanks to the application of our control method, it was possible to exclude the 95% of fibres found in samples from the assessment. Moreover, we compared fibres abundances observed in samples and controls. This study, combining an approach for minimizing the bias associated to airborne fibre contamination, provided a reliable assessment of marine litter ingestion in demersal elasmobranchs.

Revision of the Eocene ‘Platyrhina’ species from the Bolca Lagerstätte (Italy) reveals the first panray (Batomorphii: Zanobatidae) in the fossil record

The fossil-Lagerstätte of Bolca (Italy) is well known for the diversity and exquisite preservation of its bony and cartilaginous fishes documenting tropical shallow-water marine environments associated with coral reefs in the western Tethys during the early Eocene. In this study, the taxonomic, systematic and phylogenetic position of two batoid species traditionally assigned to the living thornback ray genus Platyrhina is re-evaluated. †Platyrhina bolcensis Heckel, 1851 is recognized as a separate species of the Platyrhinidae because of its plate-like antorbital cartilage with an irregular outline and a small horn on the nasal capsules. Also, the rostral cartilage does not reach the anterior border of the disc. Support for the placement of this species within the new genus †Eoplatyrhina gen. nov. is based on a combination of morphological and meristic features (e.g. nasal capsules at right angles to the rostrum; large space between the hyomandibulae and mandibular arch; approximately 132 vertebral centra; 15–16 rib pairs; 81–87 pectoral radials; 18–21 pelvic radials; short, straight and stout claspers; 40–50 caudal-fin radials; thorns absent). A second species, †Platyrhina egertoni (De Zigno, 1876), is more closely related to the living panray Zanobatus than Platyrhina and is assigned here to †Plesiozanobatus gen. nov. because of a combination of characters that support its placement within the family Zanobatidae (tail stout and short, distinctly demarcated from disc; two dorsal fins and complete caudal fin; small dermal denticles and scattered thorns covering disc and tail; rostral cartilage absent; nasal capsules without horn-like processes; mesopterygium absent). The systematic position of a third taxon, †Platyrhina gigantea (Blainville, 1818), is currently impossible to establish due to the poor preservation of the only known specimen, and therefore we propose to consider it a nomen dubium. Palaeoecological and biogeographic features of the Eocene platyrhinids and zanobatids from Bolca are also discussed.http://zoobank.org/urn:lsid:zoobank.org:pub:B4C7A979-7972-409B-B489-A6DDD5E35FE5

Evaluating the effectiveness of management measures on skates in a changing world

Global declines in elasmobranchs have been observed. Conservation measures such as area closures and fisheries prohibitions have been put in place to support the recovery of vulnerable species. However, the effectiveness of such measures is rarely evaluated in the context of other factors that may affect population abundance. This study investigates the effectiveness of management measures using 1) General additive mixed model derivative changes, taking into account environmental factors that may affect population stochasticity and 2) an age-structured density dependent population dynamic model. The Raja undulata (undulate ray) 2009 targeted fisheries prohibition was used as a case study. Potential beneficial responses on sympatric species Raja clavata (thornback ray) were modelled.A significant increase in abundance was observed in both IUCN red list species during the ban. Surface seawater temperature had a marginal effect on the abundance of both species. The prohibition was in place for an insufficient length of time for long lasting effects to be detected on skate length. The population dynamic model indicated that the increase in abundance was only possible when combining the fisheries ban with increased juvenile discard survival. Our results indicate that species conservation measures may not only have positive effects on the species in question, but also on species with a niche overlap. Nonetheless, due to ongoing fishing for other species, the full potential of fisheries prohibitions may not be realised. For real benefits to be assessed, evaluation of bans should take place once a steady state is observed.

Light and Scanning Electron Microscopic Observations on Grillotia erinaceus (Cestoda: Trypanorhyncha)

In the present study, the plerocercoids of Grillotia erinaceus were obtained from the wall of the anterior oesophagus, stomach, pyloric caeca and liver of teleost Black Sea whiting Merlangius merlangus and adults were collected from the intestine of elasmobranch thornback rays Raja clavata caught by commercial fishing vessels off Sinop, Turkey. Standard parasitological investigation methods were applied and morphological diagnostic features of the whole parasite, bothria, scolex, tentacular armatures and tentacles were studied in detail using a light and Scanning Electron Microscope (SEM). The plerocercoids of this parasite had a total length of 5.96 mm on average and this was 21.6 mm on average in adults. The measurement data of all morphological diagnostics are provided and photomicrographs of each part of the parasite are presented. This study also provides the detailed morphological features of both plerocercoids and adults of G. erinaceus in M. merlangus and R. clavata for the first time in the Turkish coasts of the Black Sea.&nbsp;&nbsp;