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Jim R. Ellis - One of the best experts on this subject based on the ideXlab platform.

  • Angel Sharks (Squatinidae): A review of biological knowledge and exploitation.
    Journal of fish biology, 2021
    Co-Authors: Jim R. Ellis, Joanna Barker, Eva Meyers, Sophy R. Mccully Phillips, Michelle R. Heupel
    Abstract:

    Angel Sharks (Squatina spp.) are distributed in warm temperate to tropical waters around the world. Many species occur in shelf seas and exhibit seasonal inshore-offshore migrations, moving inshore to give birth. Consequently, there can be high spatial overlap of Angel Shark populations with fisheries and other human activities. Their dorso-ventrally flattened body shape, large size (most species attain >100 cm total length, LT ) and demersal nature means that they may be taken in a variety of demersal fishing gears from birth. Available data indicate that Angel Sharks typically have a biennial reproductive cycle, with litter sizes generally

  • Extinction risk and conservation of critically endangered Angel Sharks in the Eastern Atlantic and Mediterranean Sea
    ICES Journal of Marine Science, 2019
    Co-Authors: Julia M. Lawson, Riley Pollom, Cat Gordon, Joanna Barker, Eva Meyers, Heike Zidowitz, Jim R. Ellis, Alex Bartolí, Gabriel Morey, Sarah Fowler
    Abstract:

    Abstract Understanding the details of local and regional extinctions allows for more efficient allocation of conservation activities and resources. This involves identifying where populations persist, where populations may still be present, and where populations may be locally extinct. Three threatened Angel Sharks occur in the Eastern Atlantic and Mediterranean Sea: Sawback AngelShark (Squatina aculeata), Smoothback AngelShark (Squatina oculata), and AngelShark (Squatina squatina). Population sizes and geographic ranges of these species have been reduced due to overfishing and habitat loss, placing them among the world s most threatened chondrichthyans. We revise distribution maps, review global status, and present a Conservation Strategy to protect and restore these Angel Shark populations by minimizing fishing mortality, protecting critical habitat, and mitigating human disturbance. Updated distributions reveal that a halving of the geographic extent may have occurred for all three species, with potential declines of 51% for Sawback AngelShark, 48% for Smoothback AngelShark, and 58% for AngelShark. While 20 national and international management measures are now in place for AngelShark, only half of these include the other two species. We encourage further conservation action to adopt and develop this Conservation Strategy to restore Angel Shark populations to robust levels and safeguard them throughout their range.

  • Having confidence in productivity susceptibility analyses: A method for underpinning scientific advice on skate stocks?
    Fisheries Research, 2015
    Co-Authors: Sophy R. Mccully Phillips, Finlay Scott, Jim R. Ellis
    Abstract:

    Abstract National and European Shark conservation plans aim to manage elasmobranch stocks sustainably. However uncertainties and deficiencies with available data hamper traditional, quantitative assessment methods of stock status to inform those plans, and thus effective management. The International Council for the Exploration of the Sea (ICES) Expert Groups have explored a range of data deficient assessment methods that may be used to support management advice, including Productivity Susceptibility Analysis (PSA). This method was applied to the demersal elasmobranch fauna (21 species) of the Celtic Sea to explore how such approaches could inform the management of skates (Rajidae). This species complex is an important catch component for demersal trawl and gillnet fisheries and is currently managed under a mixed species total allowable catch (TAC). PSAs were conducted on both of these fisheries, by four experts from three countries to introduce independence, and to quantify the range in perceptions of each stock. Confidence scoring of attributes was incorporated and probability distributions generated to model uncertainty in the expert responses to susceptibility attributes. Results showed that three Shark species (tope, Galeorhinus galeus; Angel Shark, Squatina squatina and spurdog, Squalus acanthias) were the most vulnerable species in both fisheries (a consequence of their life history strategy and large size), followed by two skates (otter trawl) and three skates (gillnet). All of these species have some form of restrictive management and, apart from tope, are either currently listed as prohibited species or have a zero TAC in the area. Blonde ray, Raja brachyura was ranked as the next most vulnerable member of the commercially exploited skate complex. This adaptation of the PSA approach enabled skate species of higher and lower risk to be ranked and thus inform where management efforts should be focussed, whilst giving a novel consideration to uncertainty through canvassing expert opinion.

  • Changes in the demersal fish assemblages of British coastal waters during the 20th century
    ICES Journal of Marine Science, 2000
    Co-Authors: Stuart I. Rogers, Jim R. Ellis
    Abstract:

    Catches of demersal fish from research vessel surveys in three areas around the British Isles from 1901 to 1907 were compared with survey catches in the same areas from 1989 to 1997. Mesh size and other characteristics of the trawls used suggested that some of these data were comparable, and could be used to describe changes in demersal fish assemblages over the last 80 years. In Start Bay (NW English Channel) and the Irish Sea, species diversity was the same in both periods, although the most abundant species in each period were not the same. In English coastal regions of the southern North Sea, fish populations became more diverse, as plaice Pleuronectes platessa and whiting Merlangius merlangus became less abundant, and the relative abundance of several non-target species such as dragonet Callionymus spp., bib Trisopterus luscus, and bull-rout Myoxocephalus scorpius increased. The proportion in the catch of small fish species (maximum body length 30 cm) in catches decreased in all regions during the time period, except in the Irish Sea where plaice replaced grey gurnard Eutrigla gurnardus as a dominant species. There was a decline in abundance of large Sharks, skates and rays, including the common skate, Raja batis, white skate R. alba and the Angel Shark Squatina squatina. During historic surveys, 60% of the elasmobranch fauna consisted of thornback ray Raja clavata, whereas in contemporary surveys the lesser spotted dogfish Scyliorhinus canicula was the most abundant elasmobranch. Changes in length-frequency distribution of fish in both target and non-target categories, and other observed changes, were thought to be a response to commercial exploitation, and corresponded to similar observations recorded elsewhere. (C) 2000 British Crown Copyright.

Jürgen Kriwet - One of the best experts on this subject based on the ideXlab platform.

  • Development and evolution of tooth renewal in neoselachian Sharks as a model for transformation in chondrichthyan dentitions.
    Journal of anatomy, 2018
    Co-Authors: Moya Meredith Smith, Jürgen Kriwet, Charlie J. Underwood, Brett Clark, Zerina Johanson
    Abstract:

    A defining feature of dentitions in modern Sharks and rays is the regulated pattern order that generates multiple replacement teeth. These are arranged in labio-lingual files of replacement teeth that form in sequential time order both along the jaw and within successively initiated teeth in a deep dental lamina. Two distinct adult dentitions have been described: alternate, in which timing of new teeth alternates between two adjacent files, each erupting separately, and the other arranged as single files, where teeth of each file are timed to erupt together, in some taxa facilitating similarly timed teeth to join to form a cutting blade. Both are dependent on spatiotemporally regulated formation of new teeth. The adult Angel Shark Squatina (Squalomorphii) exemplifies a single file dentition, but we obtained new data on the developmental order of teeth in the files of Squatina embryos, showing alternate timing of tooth initiation. This was based on micro-CT scans revealing that the earliest mineralised teeth at the jaw margin and their replacements in file pairs (odd and even jaw positions) alternate in their initiation timing. Along with Squatina, new observations from other squalomorphs such as Hexanchus and Chlamydoselachus, together with representatives of the sister group Galeomorphii, have established that the alternate tooth pattern (initiation time and replacement order) characterises the embryonic dentition of extant Sharks; however, this can change in adults. These character states were plotted onto a recent phylogeny, demonstrating that the Squalomorphii show considerable plasticity of dental development. We propose a developmental-evolutionary model to allow change from the alternate to a single file alignment of replacement teeth. This establishes new dental morphologies in adult Sharks from inherited alternate order.

  • On the occurrence of the Taiwan Angel Shark, Squatina formosa Shen & Ting, 1972 (Chondrichthyes, Squatinidae) from Japan
    Zoosystematics and Evolution, 2010
    Co-Authors: Jürgen Kriwet, Hiromitsu Endo, Björn Stelbrink
    Abstract:

    In the Pacific, most Angel Sharks display rather limited geographic distributions. Recent findings of three specimens of the Taiwan Angel Shark, Squatina formosa, from Tosa Bay, Kochi Prefecture, Japan enlarges the known geographic range of this species considerably. So far, this species only has been known from Taiwan. Other records might be considered misidentifications. The three specimens that form the focus of this study are from the central Tosa Bay (Province of Kochi) in SE Japan. They were collected with otter trawls in ca. 200 m depth in May and June 2008. Although these specimens differ slightly from the holotype from Taiwan in some features, their identification as belonging to Squatina formosa is well supported by the colour pattern and a suite of morphological characters such as shape and meristics of the upper lip arch, the shape of the caudal fin lobe and the shape and size of the pectoral, pelvic and dorsal fins. Additionally, the taxonomic identification is strongly supported by molecular and data by comparison with a specimen from Taiwan and previously published data. The mtDNA difference between the Taiwanese and Japanese populations is 0.2 % and is most likely related to a descent from a postulated original population some 10,000 years ago. It is most likely that this species occurs from the small Batan Islands, along the Ryukyu Trench and the corresponding Ryukyu Islands from Taiwan north along the south-eastern mainland coast of Japan. This species seemingly occurs along the Kuroshio Current and is absent from cold-influenced waters (e.g. western Taiwan, China and Japan seas). The recent finding of this species in Tosa Bay most probably is due to range extension because of globally increasing sea water temperatures.

  • on the occurrence of the taiwan Angel Shark squatina formosa shen ting 1972 chondrichthyes squatinidae from japan
    Zoosystematics and Evolution, 2010
    Co-Authors: Jürgen Kriwet, Hiromitsu Endo, Björn Stelbrink
    Abstract:

    In the Pacific, most Angel Sharks display rather limited geographic distributions. Recent findings of three specimens of the Taiwan Angel Shark, Squatina formosa, from Tosa Bay, Kochi Prefecture, Japan enlarges the known geographic range of this species considerably. So far, this species only has been known from Taiwan. Other records might be considered misidentifications. The three specimens that form the focus of this study are from the central Tosa Bay (Province of Kochi) in SE Japan. They were collected with otter trawls in ca. 200 m depth in May and June 2008. Although these specimens differ slightly from the holotype from Taiwan in some features, their identification as belonging to Squatina formosa is well supported by the colour pattern and a suite of morphological characters such as shape and meristics of the upper lip arch, the shape of the caudal fin lobe and the shape and size of the pectoral, pelvic and dorsal fins. Additionally, the taxonomic identification is strongly supported by molecular and data by comparison with a specimen from Taiwan and previously published data. The mtDNA difference between the Taiwanese and Japanese populations is 0.2 % and is most likely related to a descent from a postulated original population some 10,000 years ago. It is most likely that this species occurs from the small Batan Islands, along the Ryukyu Trench and the corresponding Ryukyu Islands from Taiwan north along the south-eastern mainland coast of Japan. This species seemingly occurs along the Kuroshio Current and is absent from cold-influenced waters (e.g. western Taiwan, China and Japan seas). The recent finding of this species in Tosa Bay most probably is due to range extension because of globally increasing sea water temperatures.

Abitia Cárdenas, Leonardo Andrés - One of the best experts on this subject based on the ideXlab platform.

  • Trophic level and isotopic composition of 13C and 15N of pacific Angel Shark, Squatina californica (Ayres, 1859), in the Southern Gulf of California, Mexico
    'Tropical Journal of Fisheries and Aquatic Sciences', 2011
    Co-Authors: Escobar Sánchez Ofelia, Galván Magaña Felipe, Abitia Cárdenas, Leonardo Andrés
    Abstract:

    δ13C and δ1NN stable isotopes were used to determine trophic level and the assimilated food components of Pacific Angel Shark, Squatina californica and its variation between size, sexes and seasonally in the southern Gulf of California, Mexico. Muscle tisúes were collected during 2001 to 2003. The quantification of δ13C and δ15N stable isotopes was realizad by isotope ratio mass spectrometry. The values of stable isotope of carbon (δ13C) ranged from -16.55 to -15.06% (average -15.94% + 0.34) and nitrógeno (δ15N) was between 18.30 to 19.52% (verage 18.90 + 0.27), we found that as male and female feeds on same zones and not differences were found years and seasons, therefore the Angel Shark present a same throphic level to feed on benthic prey in the coast zone. The trophic level was determined for S. californica with 4.5, therefore is considered a tertiary consumer in the Routh Gulf of California. We concluded that Pacific Angel Shark present a same trophic pattern Turing migration to deep areas in the Gulf of California, feeding on benthic species with same trophic level

Christian Capape - One of the best experts on this subject based on the ideXlab platform.

  • Türkiye Sularında (Doğu Akdeniz) Keler Balığının Squatina squatina(Chondrichthyes: Squatinidae) Bulunuşu ve Biyolojik Gözlemler
    2015
    Co-Authors: Okan Akyol, Vahdet Ünal, Christian Capape
    Abstract:

    Bu çalışmada, Türkiye sularında keler balığının, Squatina squatina (Linnaeus, 1758) yeni bir kaydı rapor edilmektedir. Türk sularından S. squatina'nın önceki av kayıtlarının derlenmesi bu türün göreceli nadirliğini göstermektedir. Aynı zamanda Gökova Körfezi, S. squatina'nın gebeliği nedeniyle Türkiye kıyıları boyunca bu balık için bir üreme alanı olabilir.A new record of Angel Shark Squatina squatina (Linnaeus, 1758) in Turkish waters is reported in this note. A review of previous catch records of S. squatina from Turkish waters show that the species is relatively rare in the area. However, the observed specimen was a pregnant female suggesting that Gökova Bay could be a spawning area for S. squatina in the Turkish coas

  • Reproductive biology of the smoothback Angel Shark, Squatina oculata (Elasmobranchii: Squatinidae), from the coast of Senegal (eastern tropical Atlantic)
    Journal of the Marine Biological Association of the United Kingdom, 2002
    Co-Authors: Christian Capape, A. A. Seck, A. Gueye-n'diaye, Y. Diatta, M. Diop
    Abstract:

    Two species of genus Squatina were recorded off the coast of Senegal and Squatina oculata is the most commonly caught in the area. Adult males and females studied were over 820 and 890 mm total length (TL) respectively, with the largest male and the largest female recorded being 1450 mm and 1570 mm and weighed 37 kg and 39 kg respectively. The females were significantly heavier than the males. Size at birth was between 226 and 266 mm and weight at birth between 129 and 159 g. Weight of ripe oocytes ranged from 87·65 to 117·60 g (mean SD 101·73±&;8·65). Gestation lasts one year minimum. Squatina oculata is a lecithotrophic species. Counts of ripe oocytes, eggs, embryos and fully developed foetuses showed that ovarian fecundity is significantly higher than uterine fecundity. The former ranged from 8 to 20 (mean SD 12·04±5·80), the latter from 3 to 8 (mean SD 6·22±3·41). There is no relationship between size and the categories of fecundity. Adult males and females were more common than the other categories of specimens landed. Among adults, females were more numerous than males, mainly gravid specimens.

Francesco Tiralongo - One of the best experts on this subject based on the ideXlab platform.

  • Integrating local ecological knowledge, citizen science and long‐term historical data for endangered species conservation: Additional records of Angel Sharks (Chondrichthyes: Squatinidae) in the Mediterranean Sea
    Aquatic Conservation: Marine and Freshwater Ecosystems, 2019
    Co-Authors: Ioannis Giovos, Vasilis-orestis Stoilas, Sara A. A. Almabruk, Nikolaos Doumpas, Philippos Marakis, Mary Maximiadi, Dimitrios K. Moutopoulos, Periklis Kleitou, Ioannis Keramidas, Francesco Tiralongo
    Abstract:

    All three species of Angel Sharks (genus Squatina) inhabiting the Mediterranean Sea are listed as Critically Endangered in the International Union for Conservation of Nature Red List of Threatened Species due to overexploitation. New records from Cyprus, Greece, Italy and Libya were collected from citizen‐scientists and integrated with local knowledge obtained using structured interviews in the four countries. Observations and reports, together with an analysis of the reconstructed fisheries data, resulted in the identification of areas of interest, a review of the illegal trade of the species and a debate about the credibility of fisheries data for assessing threatened and/or protected species. Unconventional sources of information, such as social media, were identified as important tools for monitoring rare and endangered marine wildlife. This work will contribute to promoting international cooperation for advancing Angel Shark conservation in line with the Eastern Atlantic and Mediterranean Angel Shark Conservation Strategy.