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Spatial distribution of all MEDLEM records.

Spatial distribution of all MEDLEM records.

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The Mediterranean Large Elasmobranchs Monitoring (MEDLEM) database contains over 3000 records (more than 4000 individuals) of large elasmobranch species from 20 different countries around the Mediterranean and Black seas, observed from 1666 to 2017. The main species included in the archive are the devil fish (1 813 individuals), the basking shark (...

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... information' spatial coverage is more complete and more capillary in the Adriatic, Tyrrhenian, Aegean and Balearic seas and the Strait of Sicily. The south-central and south-western Mediterranean sectors provided less information, probably as a result of lower coverage of the collaborative research centres (Fig. 2). The great white shark (C. carcharias) has been reported throughout the Mediterranean with greater frequency in the northern Adriatic Sea (FAO-GFCM's Geographic Sub Area [GSA] 17), Straits of Sicily (GSA 16) and Tyrrhenian Sea (GSA9). It is also reported from Tunisian waters (Bradaï & Saidi, 2013), Turkish waters and the Marmara Sea ...
Context 2
... information' spatial coverage is more complete and more capillary in the Adriatic, Tyrrhenian, Aegean and Balearic seas and the Strait of Sicily. The south-central and south-western Mediterranean sectors provided less information, probably as a result of lower coverage of the collaborative research centres (Fig. 2). The great white shark (C. carcharias) has been reported throughout the Mediterranean with greater frequency in the northern Adriatic Sea (FAO-GFCM's Geographic Sub Area [GSA] 17), Straits of Sicily (GSA 16) and Tyrrhenian Sea (GSA9). It is also reported from Tunisian waters (Bradaï & Saidi, 2013), Turkish waters and the Marmara Sea ...

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Abstract The Mediterranean Large Elasmobranchs Monitoring (MEDLEM) database contains more than 3,000 records (with more than 4,000 individuals) of large elasmobranch species from 21 different countries around the Mediterranean and Black seas, observed from 1666 to 2017. The principal species included in the archive are the devil ray (1,868 individu...

Citations

... According to the MEDITS surveys carried out in the Mediterranean between 2016 and 2018, both S. aculeata and S. oculata were absent (Anonymous 2017(Anonymous , 2019. The database of the Mediterranean Large Elasmobranchs Monitoring (MEDLEM) showed that both angelshark species considered to reside there were very rare throughout the whole basin (Mancusi et al. 2020). ...
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All three species of angelsharks that inhabit the Mediterranean Sea, Squatina aculeata Cuvier, 1829; Squatina oculata Bonaparte, 1840; and Squatina squatina (Linnaeus, 1758), are classified as Critically Endangered on the IUCN Red List of Threatened Species, since their populations have suffered severe decline and range reduction, mainly due to fishing pressure. The presently reported study aims to further update records of S. aculeata and S. oculata in the basin in order to achieve a clearer picture of their current status and geographical distribution. In this way, we were able to add a contribution to our knowledge about their biological characteristics. Records on the incidental capture and observation of specimens of S. aculeata and S. oculata between 2005 and 2022 were collected through the input of alerted professional fishermen, fisher amateurs, and specialist observers on fishery landings or on board in the context of specific surveying programs as well as of citizens' science initiatives. Biological characters such as total length, total weight, sex, and maturity were determined whenever possible. A total of 18 S. aculeata and 34 S. oculata specimens were recorded. Data corroborate the current occurrence, which is almost rare, of these two Critically Endangered elasmobranchs from the central to the east part of the basin, revealing furthermore the presence of S. aculeata in Sardinian waters, in the western part of the basin. Data document the important habitats for both species existing in the Strait of Sicily, especially in the area around Malta, and confirm the occurrence of S. aculeata in the southern Aegean Sea. The current presence of both species is also established in Mediterranean Egyptian waters. Our study suggests the urgent need for a wider application and/or reinforcement of existing protection measures for these angelshark species and their habitat, including populations of the southern Mediterranean waters.
... In the present study, a thorough review of anecdotal references related to shark presence aims to evaluate shark-human interactions in the Greek waters during the early and developmental phase of the fisheries (1900-early 1980s). This effort will close the historical gap in knowledge on shark populations in the Eastern Mediterranean [11,12], and the data gathered could be used in the MEDLEM database, a repository of information on large elasmobranchs in the Mediterranean and Black seas [13]. It can also be used in assessments for the Red List by the International Union for Conservation of Nature (IUCN), which helps to understand the historical presence and distribution of species. ...
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The lack of historical data on shark presence, distribution, and status in the Eastern Mediterranean undermines efforts to manage and protect their populations. An exhaustive review of anecdotal references related to shark presence during the early and development phase of Greek fisheries (1883–1983) was conducted. In the early-20th century (1912), the first sighting of the presence of a dead shark was reported in the Ionian Sea. Later on, the presence of sharks gradually increased up to 1969, with most records being more frequent for the Aegean Sea, whereas the number of sharks being sighted declined leading up to the middle of 1980s. The increase in shark attacks during the mid-20th century led to a calling for culling of sharks in co-operation with the competent authorities promoting the permission to hunt sharks with firearms and offering rewards for killed individuals. A high number of these observations potentially resulted from shark attacks on people, whereas this is not currently evident. This is an indicator of the lower abundance of sharks in modern times and subsequently an alteration in the way that our current modern society is approaching the protection of such vulnerable species.
... the near threatened sharpnose sevengill shark (Heptranchias perlo). In addition to these reviews, there is also a new data collection project, the Mediterranean Large Elasmobranchs Monitoring Program (MEDLEM), aiming to contribute to biodiversity management and conservation of the Mediterranean basin [61]. Chondrichthyans of the Mediterranean Sea have been described as "Endangered", "Vulnerable" and "Data deficient" by the IUCN Shark Specialist Group [17]. ...
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The Mediterranean Sea is a renowned biodiversity hotspot influenced by multiple interacting ecological and human forces. A gap analysis on the biology of Mediterranean marine fishes was conducted in 2017, revealing the most studied species and biological characteristics, as well as identifying knowledge gaps and areas of potential future research. Here, we updated this gap analysis five years later by reviewing the literature containing information on the same eight biological characteristics, namely length-weight relationships, growth, maximum age, mortality, spawning, maturity, fecundity and diet, for the 722 fish species of the Mediterranean Sea. The results revealed a considerable knowledge gap as 37% of the species had no information for any of the studied characteristics, while 13% had information on only one characteristic. Out of all the biological characteristics, the smallest knowledge gap was found in the length-weight relationships (studied for 51% of the species, mainly in the eastern Mediterranean), while the least studied characteristic was mortality (studied for 10% of the species). The western and eastern Mediterranean Sea were leading forces in data collection exhibiting the narrowest gaps between current and desired knowledge. The most studied species across the entire region were the highly commercial European hake ( Merluccius merluccius ), red mullet ( Mullus barbatus ), European anchovy ( Engraulis encrasicolus ), European pilchard ( Sardina pilchardus ), common pandora ( Pagellus erythrinus ), and annular seabream ( Diplodus annularis ). The knowledge gap has shrunk by 6% during the last five years, with 40 new species having at least one study on their biology. Moreover, research has slightly shifted towards species that have been traditionally neglected, e.g., sharks, rays and chimaeras (chondrichthyans). It is recommended that research becomes less focused on commercial species and more targeted towards the identified gaps, vulnerable species (e.g., deep-sea species and chondrichthyans) and species that could potentially pose a threat (e.g., non-indigenous species) to the ecosystems of the everchanging Mediterranean Sea.
... The Mediterranean Sea is one of the world's hotspot for marine biodiversity but is threatened by cumulative human impacts (Micheli et al., 2013). Being in particular a hotspot for elasmobranchs, with more than 80 species described there (Mancusi et al., 2020), the Mediterranean Sea is unfortunately considered by the International Union for Conservation of Nature (IUCN) among the three global biodiversity hotspots where elasmobranchs are severely threatened. In this basin, at least the 65% of elasmobranch species and of that 50% of the recorded species of rays are facing elevated risk of extinction (i.e., population status classified as Vulnerable, Endangered, or Critically Endangered) (Dulvy et al., 2016). ...
Article
The Mediterranean Sea is among the three biodiversity hotspots of the world where elasmobranchs are severely threatened. Elasmobranchs act as apex or meso-predators within marine food webs and the loss/decline of apex predators determines the mesopredator release, leading in turn to increased predation on smaller prey. However, also several mesopredators (including rays, skates and small sharks) are intensively fished, being of commercial interest, or by-caught, and thus mesopredators increase could not be so evident. We analysed the trophic ecology of an endemic Mediterranean ray, the starry ray Raja asterias, at a seasonal scale from the Adriatic basin, one of the most intensively exploited area of the Mediterranean, by means of stomach contents and stable isotopes analyses. Our results evidenced that starry rays rely on benthic sources including species of local commercial values, such as swimming crabs, small cephalopods, and stomatopods and share the same trophic position with other elasmobranchs (rays, skates, and small sharks) and other mesopredators (e.g., common soles, Norway lobsters and mullets). As all mesopredators are overexploited, as well as their benthic prey are affected by intense trawl-fishing, the whole food webs are disrupted and neither the classical trophic cascade nor the mesopredator release hypothesis could be verified. Conservation measures for these species, such as the release after capture or the application of exclusion grids to the net, should be applied in areas where populations are strongly impacted by trawling.
... However, some studies confirm the presence of nursery and spawning areas for some species such as in the Gulf of Gabes (GSA 14) in Tunisia. These critical habitats Spatial distribution of all MEDLEM records [12]. ...
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Cartilaginous fishes are a very ancient group; Sharks have lived on Earth for about 500 million years, since long before the dinosaurs. They have been able to survive and overcome five mass extinctions since their appearance. They play in fact a key role in maintaining the balance of marine ecosystems. More than 97% of the shark population has disappeared in the last two centuries. Currently, a high percentage is threatened, many are data-deficient. Many menaces face sharks, but fishing pressure seems to be most critical. This chapter focuses on the current status of cartilaginous fishes and progress on conservation measures and actions taken mainly through regional plans.
... As a bycatch species, the catch of blue sharks is intrinsically linked to abundance but also to global market demand, both being relatively complex drivers. Blue shark is amongst the most abundant shark species in international trade (Okes and Sant, 2019) for the meat and/or fins (e.g., dominant shark species for meat in Japan, Spain, Taiwan, and Uruguay: Okes and Sant, 2019;Brazil: Cruz et al., 2021;Italy: Serena and Silvestri, 2018;Mancusi et al., 2020). Overall, the importance of blue shark in the fin trade highlights its economic importance and the driver of the demand (Porcher et al., 2021). ...
... As a bycatch species, the catch of blue sharks is intrinsically linked to abundance but also to global market demand, both being relatively complex drivers. Blue shark is amongst the most abundant shark species in international trade (Okes and Sant, 2019) for the meat and/or fins (e.g., dominant shark species for meat in Japan, Spain, Taiwan, and Uruguay: Okes and Sant, 2019;Brazil: Cruz et al., 2021;Italy: Serena and Silvestri, 2018;Mancusi et al., 2020). Overall, the importance of blue shark in the fin trade highlights its economic importance and the driver of the demand (Porcher et al., 2021). ...
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Blue shark (Prionace glauca) is amongst the most abundant shark species in international trade, however this highly migratory species has little effective management and the need for spatio-temporal strategies increases, possibly involving the most vulnerable stage or sex classes. We combined 265,595 blue shark observations (capture or satellite tag) with environmental data to present the first global-scale analysis of species’ habitat preferences for five size and sex classes (small juveniles, large juvenile males and females, adult males and females). We leveraged the understanding of blue shark biotic environmental associations to develop two indicators of foraging location: productivity fronts in mesotrophic areas and mesopelagic micronekton in oligotrophic environments. Temperature (at surface and mixed layer depth plus 100 m) and sea surface height anomaly were used to exclude unsuitable abiotic environments. To capture the horizontal and vertical extent of thermal habitat for the blue shark, we defined the temperature niche relative to both sea surface temperature (SST) and the temperature 100 m below the mixed layer depth (Tmld+100). We show that the lifetime foraging niche incorporates highly diverse biotic and abiotic conditions: the blue shark tends to shift from mesotrophic and temperate surface waters during juvenile stages to more oligotrophic and warm surface waters for adults. However, low productivity limits all classes of blue shark habitat in the tropical western North Atlantic, and both low productivity and warm temperatures limit habitat in most of the equatorial Indian Ocean (except for the adult males) and tropical eastern Pacific. Large females tend to have greater habitat overlap with small juveniles than large males, more defined by temperature than productivity preferences. In particular, large juvenile females tend to extend their range into higher latitudes than large males, likely due to greater tolerance to relatively cold waters. Large juvenile and adult females also seem to avoid areas with intermediate SST (~21.7-24.0°C), resulting in separation from large males mostly in the tropical and temperate latitudes in the cold and warm seasons, respectively. The habitat requirements of sensitive size- and sex-specific stages to blue shark population dynamics are essential in management to improve conservation of this near-threatened species.
... accessed on 1 May 2020) facilitate access to species records. Advances in social media and mobile-phone applications have strengthened citizen science [13], providing extensive information about occurrence data in several phylogenetic groups, including chondrichthyans [9,[14][15][16][17][18][19]. The use of internet and crowdsourcing platforms for ecology (also known as "iEcology") moves beyond traditional research studies and generates data about ecological patterns and processes (e.g., species occurrences, distributional range shifts) from digitally stored sources that would otherwise be unavailable [20,21]. ...
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Chondrichthyans are apex predators influencing the trophic web through a top-down process thus their depletion will affect the remaining biota. Notwithstanding that, research on chondrichthyans is sparse or data-limited in several biogeographic areas worldwide, including the Levantine Sea. We revise and update the knowledge of chondrichthyans in Cyprus based on a bibliographic review that gains information retrieved from peer-reviewed and grey literature, Global Biodiversity Information Facility (135 records of at least 18 species) and the Ocean Biodiversity Information System (65 records of at least14 species), and the citizen science project Mediterranean Elasmobranchs Citizen Observations (117 records per 23 species). Our updated checklist reports 60 species that account for about 70% of the Mediterranean chondrichthyan biota. The list includes 15 more species than the previous checklist and our study reports three new species for Cyprus waters, namely the blackmouth catshark Dalatias licha, the round fantail stingray Taeniurops grabatus, and the sawback angelshark Squatina aculeata. Our research highlights the need for conservation measures and more studies regarding the highly threatened blackchin guitarfish Glaucostegus cemiculus and the devil ray Mobula mobular, and stresses the importance for training a new generation of observers to strengthen the knowledge and conservation of elasmobranchs in the region.
... Some species are now found only at great depths (400-500 m) and in small numbers, such as Heptranchias perlo and Galeorhinus galeus. G. galeus is considered rare in the Northern Adriatic [21], while H. perlo is classified as data-deficient by the MEDLEM database, with only 10 reported individuals in the whole Mediterranean [22]. However, H. perlo inhabits depths where it is difficult for commercial fisheries to reach another very rare large selachian, Squatina squatina, but catches are still occasionally reported [23]. ...
... Regarding the species composition, even though the ratio of selachians in bottom trawl catches has been significantly reduced since the 1970s, cartilaginous species are still regularly represented, especially S. canicula, Squalus spp. and Raja species, which have been drastically reduced in many Mediterranean areas [22]. This is a positive indication of the state of demersal communities and biodiversity in Montenegrin waters, and provides a rare opportunity to at least attempt to maintain the current state, if not even to devise a strategy to reverse the process and preserve the treasures that remain still under the surface. ...
Chapter
This study focuses on the historical data from the “HVAR” Expedition, i.e. the M/V “HVAR” cruise researches into fisheries biology in the open Adriatic, carried out in 1948–1949. These results are still of great importance for the Adriatic, even today, 71 years after the conclusion of the expedition, as they provide a unique insight into the state of fishery resources before the mass exploitation of the second half of the twentieth century. The most represented species in the catches by weight were M. merluccius, R. clavata, S. canicula, A. sphyraena and Z. faber. The significant presence of chondrichthyan species is noted, as is the absence of deep-water pink shrimp, P. longirostris, which is the dominant species in bottom trawl fisheries today. A comparison between “HVAR”, two other historical surveys (“BIOS” 1961, and “GORICA”, 1973) and MEDITS survey of 2018, shows a decrease in chondrichthian species and Catch per Unit of Effort (CPUE; kg/h), with a recent increase in P. longirostris abundance.
... that take advantage of the information provided by citizen scientists on social media benefit shark conservation. Such efforts should connect with scientific monitoring programs, such as the Mediterranean Large Elasmobranch Monitoring database (Mancusi et al., 2020) and strive to link science with effective shark conservation in the eastern Mediterranean Sea. ...
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Sharks in the Mediterranean Sea are facing an elevated risk of extinction; several species are considered endangered and some have been reduced to such low population numbers that they are hard to detect through conventional monitoring methods. The recent emergence of new technologies, such as social media, makes it easier to collect and transmit information that may contribute to the conservation of endangered species. From 2017 – 2019 we carried out a project in Greece that searched social media (i.e. Facebook, Twitter and YouTube) postings with the aim of collecting data on the occurrence and basic biological parameters of sharks in the country and their interactions with fisheries. We recorded 116 social media postings referring to sharks in Greece, of which, 100 were identified to the lowest taxonomic level; sixty four percent of these postings referred to threatened sharks, while the majority of them referred to species that had not been evaluated for the Greek Red Data Book. Sharks occurred throughout the country, were often involved in negative fishery interactions and were rarely reported to have been released back to the sea. Endangered sharks were often misidentified as commercially valuable species. Our study highlights the importance of social media as a valuable tool in collecting baseline information, while identifying and/or focusing on important conservation issues about sharks in Greece.