Dasyatis Pastinaca Research Articles

Long-term co-occurrence and gregariousness in the migratory common stingray using network analysis

Aggregations and social interactions play an important role in the movement ecology of many animals, including elasmobranchs. Several of these species have shown the capability of carrying out complex social behaviours, and the importance of sociality in this taxon is being realized. Although it is a growing field of study in the case of these organisms, these processes still need to be better understood, especially to support management and conservation policies. In this study, a long-term acoustic telemetry data set collected on Dasyatis pastinaca in a coastal marine protected area was analysed. A co-occurrence network analysis was done to investigate preferential associations among individuals, revealing non-random associations among them. The analysis revealed a few strong and consistent associations that were maintained across inter-migratory periods, as this species performs seasonal migrations to a nearby estuary, suggesting temporal stability of the observed associations. Moreover, individuals had similar average positions and a generally high overlap of space use in both periods, indicating some level of site fidelity to the fully protected area. Groups of up to 64% of tagged individuals were co-detected at a same receiver, particularly in the western side of the array. Despite our limited sample size, likely underestimating associations, these results show that in addition to their large-scale movement pattern, D. pastinaca is likely to also present active partner preference and spatial structure at a finer spatial scale. The nature of such results is relevant to support the protection of these species.

Age Readings and Assessment in Coastal Batoid Elasmobranchs from Small-Scale Size-Selective Fishery: The Importance of Data Comparability in Multi-Specific Assemblages

The large variation in vertebral shape and calcification observed among elasmobranch species prevents using a single method for enhancing growth bands and reading age. Further, estimating age and growth parameters can be difficult or impractical when samples are incomplete due to the bycatch of a size-selective fishery. Using a single and rapid method, age readings were obtained on the vertebrae of four batoid species, namely 53 individuals of Dasyatis pastinaca, 51 of Raja asterias, 15 of Torpedo marmorata, and 55 specimens of Torpedo torpedo, from the local small-scale trammel net fishery in the coastal waters (5–20 m depth) of the Central Tyrrhenian Sea during 2019–2021. Based on these data, a statistical routine was developed to obtain multiple estimates of age and growth parameters for incomplete samples due to size-selective fishing. The acceptable agreement between and within readers (intra and inter-reader disagreement < 5%) and the rate of increase in vertebral size with body size (differently ranked across species) demonstrated the consistency of the enhancing method. The parameters estimated by the Von Bertalanffy and Gompertz growth models matched the data available in the Mediterranean Sea for the species studied, with D. pastinaca, T. torpedo, and R. asterias showing the lowest (k = 0.05–0.12), intermediate (k = 0.112–0.19), and highest (k = 0.18–0.23) growth rates, respectively, in line with the life history traits of these species. Overall, the method proved effective both in delineating band pairs in vertebrae of different species and in reliably estimating the age and growth parameters of problematic samples due to size-selective fishing. The proposed method supports the collection of comparable demographic data from other areas where similar multi-specific assemblages are bycatch of size-selective fisheries impacting potential nursery areas and other essential habitats for elasmobranchs.

Using opportunistic data to study the distribution and abundance of a warm water elasmobranch at the northern edge of its range

Abstract Detecting changes in the distribution and abundance of marine species that are cryptic or occurring in very low abundances is difficult, but essential for assessing their status and informing management. One way of quantifying these changes is through the collation of opportunistic records. We reconstruct the population trajectory and distribution of the common stingray Dasyatis pastinaca around Great Britain, using opportunistic records, mostly obtained by recreational anglers. We tested if D. pastinaca declined in abundance and body size in response to fishing and if their distribution has shifted northwards in response to warming seas. We obtained 518 records covering the period 1838–2020. After correcting for observation effort, D. pastinaca catches reported by anglers showed no long-term trend over 50 years, but decreased from 1970 to 1995 and an increase in abundance since 1995. While records of species occurrence were found around much of Great Britain, nearly all were from south of 54° latitude, and records have contracted southwards since 2000. No trend in maximum size through time was detected. In conclusion, we did not find support for the hypothesized declines in abundance and body size or a northward shift in distribution of D. pastinaca and instead found a southward contraction.

Preliminary evidence of a potential reproductive aggregation area of the common stingray Dasyatis pastinaca (Linnaeus, 1758) (Chondrichthyes – Dasyatidae) in the Central Mediterranean Sea

Shallow and coastal aggregations of batoids are poorly documented in the Mediterranean Sea, despite being likely threatened by multiple anthropogenic pressures. We report the first observations of a potential summer reproductive aggregation of the common stingray (Dasyatis pastinaca). The recurrent presence in previous years of several pregnant females, a mature male and a female with fresh bite wounds was recorded in shallow waters by recreational scuba divers and scientists in Scilla Bay (Strait of Messina, Italy), a location with unique oceanographic features in the Central Mediterranean Sea. These observations suggest that the area could be used as a parturition and mating site in early summer, and this is significant for the conservation of this Vulnerable species.

Small coastal marine protected areas offer recurring, seasonal protection to the common stingray (Dasyatis pastinaca)

Marine protected areas (MPAs) are a crucial tool in safeguarding marine biodiversity. However, elasmobranchs are often not the primary protection target of MPAs, and their contribution to protect these species remains to be better understood. In this study we examine the movement patterns of common stingrays in the Professor Luiz Saldanha marine park, a Portuguese temperate coastal MPA. Using acoustic telemetry, we tagged 31 common stingrays and analyzed their spatial and temporal distribution within the MPA and adjacent areas using a long-term data set. Our findings indicate that this species exhibits seasonal site fidelity, with greater presence during the colder months and reduced presence during warmer months. Space use areas did not exceed the size of the fully protected area, and nocturnal and crepuscular activity was significantly higher than during daytime. Additionally, we observed that most individuals seasonally migrated between this MPA and the nearby Sado estuary, likely to reproduce in the latter. These results demonstrate the site fidelity of common stingrays to an area within the marine park, however the protection provided is only seasonal. Seasonal protection of the movement corridor between the marine park and the estuary would improve the management of this species.

Morphological and molecular characterization of Chloromyxum dasyatidis n. sp. (Myxosporea: Chloromyxidae) in the common stingray Dasyatis pastinaca (Linnaeus) from Tunisian waters (Central Mediterranean Sea).

A new species of Chloromyxum Mingazzini, 1890, C. dasyatidis n. sp., is described from the gallbladder of the elasmobranch fish Dasyatis pastinaca (Linnaeus) from the Mediterranean coast off Tunisia. Mature myxospores were subspherical measuring 13.0 ± 0.3 (12.5-13.9) µm in length, 11.3 ± 0.5 (10.2-12.2) µm in width, and 11.8 ± 0.5 (11.4-12.7) µm in thickness. Four pyriform polar capsules 4.4 ± 0.3 (4.0-4.9) µm long and 3.5 ± 0.3 (3.0-3.8) µm wide. Valves were ornamented by 5 to 7 elevated surface ridges and displayed short caudal filaments. Chloromyxum dasyatidis n. sp. had an overall prevalence of infection of 38.5%, with significant seasonal variation, being more prevalent during summer (60.0%) and autumn (70.8%). Phylogenetically, this species grouped within the Chloromyxum sensu stricto lineage, forming a small clade together with the genetically more similar species C. acuminatum and C. myolibati, both from stingray hosts.

Preliminary study on antimicrobial activities of skin mucus fromby-catch of Elasmobranch species

Skates and rays, which are widely encountered in the by-catch of fisheries activities from the Sea of Marmara and banned for sale by regulation, are species that are discarded if caught. For this reason, in our study, we aimed to determine the bioactive potentials of these species, considered fishing waste, by investigating the skin secretions and microbial flora. In our study, both the skin flora and mucus contents of the discarded species Dasyatis pastinaca (Linnaeus,1758), Myliobatis aquila (Linnaeus, 1758), and Raja clavata (Linnaeus, 1758) caught in the Sea of Marmara were investigated to determine their potential antimicrobial activities. A total of 164 bacteria were isolated from the epidermal mucus of the three batoid species. Antibacterial activity was observed from three isolated bacteria against Escherichia coli, Vancomycin-resistant Enterococcus faecium, E. faecalis, and Bacillus subtilis. Additionally, the highest antibacterial activity was observed for skin mucus of R. clavata. Mouse fibroblast cell viability was challenged with mucus secretions. M. aquila and R. clavata mucus secretions exhibited no observable change after 24 and 48 hours. The assays indicated that both the isolates and the skin mucus have potential antimicrobial activity against opportunistic pathogens.

Trophic ecology of three sympatric batoid species (Dasyatis pastinaca, Raja clavata, and Raja maderensis) from the Azores, NE Atlantic

Trophic ecology of three sympatric batoid species (Dasyatis pastinaca, Raja clavata, and Raja maderensis) from the Azores, NE Atlantic

Encounters with threatened batoids from the perspective of a spearfisherman suggesting an aggregation site in southeastern Aegean Sea, Turkey

Seasonal aggregations of batoids were observed in Güllük Bay (souteastern Aegean Sea) based on opportunistic underwater observations between the years of 2014–2022. Torpedo marmorata, Glaucostegus cemiculus, Dasyatis pastinaca, Gymnura altavela and Aetomylaeus bovinus were observed in the study area. The most observed species is G. altavela (n=65) and it constitutes 51.18 percent of the whole sample, and followed by A. bovinus (n=31, 24.4%), D. pastinaca (n=12, 9.44%), G. cemiculus (n=8, 6.29%) and T. marmorata (n=2, 1.57%). Based on the seasonal occurrence data of batoids observed during the research, it is seen that the species that occurred in the region from mid-spring to mid-autumn, and the aggregations peaked in July. Seasonal aggregations of batoids may have important implications for the conservation of these species. Among the observed batoids in the present study, only G. cemiculus is currently under protection in Turkey. According to EU Regulation 1343/2011 and Annex II of the Barcelona Convention, G. altavela is a prohibited species; thus, it should not be retained on board, transhipped, landed, transferred, stored, sold or displayed or offered for sale, and masters of fishing vessels shall record in the fishing logbook any event of incidental catch and release. Therefore, as an urgent measure, at least G. altavela and A. bovinus, which are considered as “critically endangered”, should be added to the list of protected species in Turkish waters, and the aggregation site in Güllük Bay should be declared as a no-take-zone during mid-spring and throughout the summer.

Proximate biochemical composition of some commercial marine fishes from Bay of Bengal, Bangladesh

Fish is known to be one of the cheapest sources of animal protein and other essential nutrients required in human diets. The knowledge of proximate biochemical composition of fishery species is fundamentally important for: the application of different technological processes, the characteristics post-mortem of species, as an aspect of quality of raw material and giving an idea of sexual stage. The study was conducted to determine the proximate biochemical composition of four marine fishes of the Bay of Bengal, Bangladesh. The study fishes were Dasyatis americana, Dasyatis pastinaca, Dasyatis zugei and Gymnothorax favagineus. From the study, it was found that Dasyatis americana contains highest protein, fat and ash concentration while Dasyatis Pastinaca holds highest concentration of moisture and lowest value of protein and fat. On the other hand, Dasyatis zugei hold lowest concentration of moisture and ash. Proximate biochemical composition of all species showed that their percentage of protein and fat content are good and can be a food item in parallel to the bony fishes.
 

Effect of ground gear modification on bycatch of rays in mediterranean bottom trawl fishery

Bycatch of rays and skates in towed fishing gears represents one of the major threats to these relatively slow-growing marine species. The objective of this study was to modify ground gear in a bottom trawl fishery to increase the escape of these species during towing without associated loss of target catch. Sea trials were carried out with a research vessel in Mersin Bay, North-eastern Mediterranean. Experimental ground gear was modified by cutting the rigging twine between the fishing line and the footrope in the central part of the ground gear. Capture of three unwanted bycatch species were estimated. The probability of capture of guitarfish (Rhinobatos sp.) and common stingray (Dasyatis pastinaca) was significantly reduced to 8% and 20% for guitarfish and stingray, respectively compared to standard ground gear. The results for spiny butterfly ray (Gymnura altavela) were inconclusive due to the wide confidence intervals. Further, the catch comparison results for five out of six target species investigated did not show significant reduction in catch efficiency when using experimental gear compared to the standard trawl. Only for common sole (Solea solea) the modified trawl had significantly lower catch efficiency than the standard trawl. We believe that this technical measure for reducing unwanted bycatch in bottom trawls has a potential to be adopted by the fishery due to being an efficient, low-cost measure which does not create additional challenges during handling of the gear.

The Length-Weight Characteristics of Five Elasmobranch Species (Pisces: Chondrichthyes) from Izmir Bay (Aegean Sea Coast of Turkey): Spring 2018

In this study, a total of 364 samples were collected and 349 of them belonged to, 349 specimens of Dasyatis pastinaca, 6 of Gymnura altavela, 5 of Torpedo marmorato, 2 of Aetomylaeus bovinus and Mustelus mustelus, were obtained by-catch in trammel nets off the Izmir Bay (Aegean sea coast of Turkey) during period of spring in 2018. Males of D. pastinaca ranged from 28–62 cm and females from 31.5-94 cm total length. The analysis of the angular coefficient (b) demonstrated that growth (in weight) in relation to length was isometric in males and females of D. pastinaca. Morphologic measurements of a total of 60 individuals to represent all individuals of the population, t test in independent groups to determine differences in males and females and all other morphometric measurements were statistically tested by multiple regression analysis (stepwise method). Therefore, difference between mean values obtained according to sexes was not found different. However, A linear correlation between weight- pelvic length for females and weight- preanal length for males according to multiple regression analysis in male and female individuals. Isometric and positive allometric growths were calculated for species of Torpedo marmorata and Gymnura altavela, respectively.

Differences in the occurrence and abundance of batoids across an oceanic archipelago using complementary data sources: Implications for conservation.

Batoids, distributed from shallow to abyssal depths, are considerably vulnerable to anthropogenic threats. Data deficiencies on the distribution patterns of batoids, however, challenge their effective management and conservation. In this study, we took advantage of the particular geological and geomorphological configuration of the Canary Islands, across an east‐to‐west gradient in the eastern Atlantic Ocean, to assess whether patterns in the occurrence and abundance of batoids varied between groups of islands (western, central, and eastern). Data were collected from shallow (<40 m, via underwater visual counts and by a local community science program) and deep waters (60–700 m, via ROV deployments). Eleven species of batoids, assessed by the IUCN Red List of Threatened Species, were registered, including three “Critically Endangered” (Aetomylaeus bovinus, Dipturus batis, and Myliobatis aquila), three “Endangered” (Gymnura altavela, Mobula mobular, and Rostroraja alba), two “Vulnerable” (Dasyatis pastinaca and Raja maderenseis), and two “Data Deficient” (Taeniurops grabata and Torpedo marmorata). Also, a “Least Concern” species (Bathytoshia lata) was observed. Overall, batoids were ~1 to 2 orders of magnitude more abundant in the central and eastern islands, relative to the western islands. This pattern was consistent among the three sources of data and for both shallow and deep waters. This study, therefore, shows differences in the abundance of batoids across an oceanic archipelago, likely related to varying insular shelf area, availability of habitats, and proximity to the nearby continental (African) mass. Large variation in population abundances among islands suggests that “whole” archipelago management strategies are unlikely to provide adequate conservation. Instead, management plans should be adjusted individually per island and complemented with focused research to fill data gaps on the spatial use and movements of these iconic species.

Venomous Animals in the Portuguese Territory: Clinical Management of Bites and Stings

There are many native species of animals with the potential to cause severe disease in Portugal. Of the four clinically relevant snake species, the vipers (Vipera latastei and Vipera seoanei) are the most concerning. They can cause severe disease and require in-hospital management, monitoring and specific treatment, including the administration of anti-snake venom serum. The Malpolon monspessulanus and Macroprotodon brevis snakes cause mostly localized clinical manifestations, which do not require specific treatment. Only a minority of the spider species in Portugal possess chelicerae (mouthparts of the Chelicerata, shaped as either articulated fangs or pincers, which may contain venom or be connected to the venom glands and are used for predation or capture of food) long enough to perforate the human skin. Nevertheless, Latrodectus tredecimguttatus and Loxosceles rufescens spider bites may require specialized treatment in a hospital setting, as well as careful active symptom surveillance. Diversely, the treatment for Scolopendra cingulata and Scolopendra oraniensis centipedes' bites is merely symptomatic. The only existing scorpion species in Portugal is the Buthus ibericus; its sting typically causes local symptoms with intense pain, and its treatment consists essentially of analgesia. The insects of the Hymenoptera order, such as bees and wasps, have the ability to inject venom into the skin. Most people present only with local or regional inflammatory response, and symptomatic treatment is usually effective. Even so, individuals with hypersensitivity to bee venom may develop anaphylaxis. Several marine species in the Portuguese coast are venomous to humans, including weeverfish (Trachinidae family), stingrays (Dasyatis pastinaca, Taeniura grabata, Myliobatis aquila), red scorpion fish (Scorpaena scrofa), cnidaria (Pelagia noctiluca, Chrysaora hysoscella, Physalia physalis) and bearded fireworm (Hermodice carunculata); treatment is symptomatic. Contact with the larvae or bristles (chitinous structures with locomotor or tactile functions) of Thaumetopoea pityocampa (pine processionary) can cause cutaneous, ocular and, rarely, respiratory reactions; its management is also symptomatic.

First record of Pteroplatytrygon violacea (Bonaparte, 1832) with annotation of cartilaginous fishes by-catch by gill nets (Egyptian Mediterranean)

Five cartilaginous fish species were recognized and identified as by-catch species during studying the catch of gill nets operated in the coastal area of Alexandria City from the Egyptian Mediterranean Waters during the study periods from Feb. 2018 to June 2018 and from Dec. 2019 to Nov. 2020. The by-catch included the first record of Pteroplatytrygon violacea, the closely related species Dasyatis pastinaca and Dasyatis tortonesei, the rarely found species Rhinoptera marginata, and the blackchin guitarfish Glaucostegus cemiculus. Among these five species, four species are listed in the IUCN Red List; as least concern for P. violacea, data deficient for D. pastinaca in the Mediterranean Sea, near threatened for R. marginata, and critically endangered for G. cemiculus. Morphological characters and morphometric measurements were studied to provide identification of these species. The species have been dissected for more biological information.

Approaching the “real” state of elasmobranch fisheries and trade: A case study from the Mediterranean

Elasmobranchs are sensitive marine species due to their K-strategic life characteristics in combination with the intensification of fisheries. Despite the regulations and conventions protecting several species, elasmobranchs are still caught as bycatch and landed throughout the Mediterranean, a location where the pressure on shark populations is well documented. Severe knowledge gaps still exist regarding their biology, ecology and the exploitation by fisheries, due to limited research and the fact that in almost all Mediterranean countries, elasmobranchs are recorded by the national authorities in aggregated landing categories. To overcome such issues, we contrasted landings and trade of elasmobranchs using an integrative sampling in auction markets, landing sites, and fish markets at three important sites in Greece, combined with DNA analysis to address mislabeling. Five species contributed more than half of the total elasmobranch catches for all fisheries combined (62.5%); Scyliorhinus canicula (21.6%) and to a lesser extent Dasyatis sp., Mustelus mustelus, Raja radula and Dasyatis pastinaca (12.8%, 11.7%, 9.6%, and 6.9% respectively). Results highlighted that small-scale fisheries underreported catches of threatened elasmobranchs. About 50–60% of the elasmobranch landings were threatened species while in the fish markets the corresponding contribution was reduced to 26%. Mislabeling was common throughout the year with several species sold under different names for increasing profit or to hinder their protection status. The current practices do not satisfy Common Fisheries Policy in terms of treacability, and the fishing of threatened elasmobranchs raises additional concerns as a conservation priority.

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 "

Characterization and comparison of the complete mitochondrial genomes of two stingrays, Dasyatis pastinaca and Dasyatis tortonesei (Myliobatiformes: Dasyatidae) from the Mediterranean Sea.

This work represents the complete mitochondrial genomes of two stingrays, Dasyatis pastinaca and Dasyatis tortonesei, from the Mediterranean Sea. The mitogenomes of these two species were obtained through whole generation sequencing and annotated. These mitogenomes were found to be 17,713bp and 17,630bp respectively and each contained 37 genes, that is 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes and two ribosomal RNA (rRNA) genes, a control region and the origin of L-strand replication (OL). All PCGs begin with the codon ATG, except for cytochrome c oxidase subunit 1 (COX1) gene, while two PCGs end with an incomplete termination codon. All tRNA genes are able to fold into their typical cloverleaf secondary structures, except for tRNA-Ser1AGY which lacks the dihydrouracil arm. The control region was 1982bp and 1889bp for D. pastinaca and D. tortonesei respectively. Phylogenetic analysis using Bayesian Inference confirmed the occurrence of the genus Dasyatis within the monophyletic subfamily Dasyatinae. This study adds on genetic resources available for these two stingray species.

Enzymatic Hydrolysis of Stingray (Dasyatis pastinaca) Muscle and Evaluation of Antioxidant and Copper Chelating Activities of the Hydrolysates

Bioactive peptides that originate from different sources, such as plant, animal, fungi, bacteria, and venom, are specific protein fragments that have positive effects on the body functions and health of living organisms. Most of the discovered bioactive peptides from different protein sources showed various biological features, such as antihypertension, antioxidant, antithrombotic, antimicrobial, and anticancer immunomodulation. The aim of this study is the evaluation of biological activities of stingray (Dasyatis pastinaca) muscle tissue protein hydrolysate. Therefore, the homogenized muscle tissue of stingray was hydrolyzed by esperase and trypsin enzymes. Enzyme/substrate ratio, hydrolysis time, and degree were optimized. Moreover, the antioxidant (CUPRAC method) and metal chelating (copper chelating) activities of the hydrolysates were evaluated.

“Urbanite” rays and sharks: Presence, habitat use and population structure in an urban semi-enclosed lagoon

There is a vital necessity to provide more biological data on rays and sharks to promote efficient conservation. In this study, we assembled a database of weekly sightings to describe temporal (seasonal) patterns in the presence of elasmobranchs within an urban, semi-enclosed, landscape (Las Canteras beach, Gran Canaria Island, eastern Atlantic). Data also provided insight into their habitat use and population structure. From October 2015 to October 2018, eight species, either endangered or “data deficient” according to the IUCN red list, were reported, including: the common eagle ray, Myliobatis aquila, the common stingray, Dasyatis pastinaca, the round stingray, Taeniurops grabatus, the spiny butterfly ray, Gymnura altavela, the bull ray, Aetomylaeus bovinus, the angel shark, Squatina squatina, the marbled electric ray, Torpedo marmorata and the hammerhead shark, Sphyrna zygaena. All species were predominantly observed at night. The species varied in their habitat use; D. pastinaca, G. altavela and S. squatina dominated in sandy and mixed bottoms, while M. aquila and T. grabatus were mostly found in rocky and mixed bottoms. Both D. pastinaca and T. grabatus did not show any seasonal pattern, with consistent records all year around. In contrast, M. aquila, G. altavela and S. squatina showed some degree of seasonality. For five species, small-sized individuals were observed. If semi-enclosed embayments at oceanic islands, under intense human presence, are used by juveniles of endangered rays and sharks, proper management, e.g. limitation of putative human interactions, need to be considered to avoid disturbances.