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Keywords = deepwater skates

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12 pages, 3054 KiB  
Article
The Fishery Biology of Two Deep-Water Skates, Bathyraja schroederi and Amblyraja frerichsi (Rajiformes: Rajidae), from the Southeast Pacific Ocean
by Carolina Vargas-Caro, María J. Indurain and Carlos Bustamante
Diversity 2024, 16(12), 709; https://doi.org/10.3390/d16120709 - 21 Nov 2024
Viewed by 576
Abstract
Chile is a biodiverse region for deep-water skates (Rajiformes), with 36 species documented in national waters, of which 73% correspond to deep-water species. Among them, the Thickbody skate (Amblyraja frerichsi) and Whitemouth skate (Bathyraja schroederi) are two poorly documented [...] Read more.
Chile is a biodiverse region for deep-water skates (Rajiformes), with 36 species documented in national waters, of which 73% correspond to deep-water species. Among them, the Thickbody skate (Amblyraja frerichsi) and Whitemouth skate (Bathyraja schroederi) are two poorly documented species with relatively high abundances. However, the current information is limited to a few specimens reported over the last 50 years between southern Brazil (SW Atlantic) and central Chile (SE Pacific). In the Southeast Pacific, both species are bycatch in the Patagonian toothfish (Dissostichus eleginoides) fishery, which operates along the Chilean coast between 800 and 1600 m of depth. This study examined aspects of demography and reproductive biology based on data from 190 specimens (125 A. frerichsi and 65 B. schroederi) obtained from the fishery in northern Chile. The new data contribute to enhancing our understanding of deep-water skate communities and highlight the vulnerability and fishing pressure experienced across their geographic distribution. Full article
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28 pages, 10889 KiB  
Article
Sibling Species Amblyraja hyperborea and A. jenseni in Slope Waters of Eastern Canada: An Ecomorphological Description
by David W. Kulka, Carolyn M. Miri, Sheila Atchison and Mark R. Simpson
Diversity 2024, 16(8), 479; https://doi.org/10.3390/d16080479 - 7 Aug 2024
Cited by 1 | Viewed by 1296
Abstract
Deepwater survey data and specimens collected from the Grand Banks to Baffin Bay in the Northwest Atlantic were used to examine the distribution, morphometrics, meristics and maturity of two siblings, Amblyraja hyperborea and A. jenseni. Our study confirmed that the two species [...] Read more.
Deepwater survey data and specimens collected from the Grand Banks to Baffin Bay in the Northwest Atlantic were used to examine the distribution, morphometrics, meristics and maturity of two siblings, Amblyraja hyperborea and A. jenseni. Our study confirmed that the two species occupy different locations, their distributions separated by Davis Strait, a biogeographic break separating Atlantic from Arctic waters. A. hyperborea with a smaller maximum size and size at maturity inhabited colder Arctic slope waters in Baffin Bay while larger A. jenseni were located in warmer Atlantic slope waters. Despite their distributional separation and thus reproductive isolation, spine counts and body morphology were almost indistinguishable between species. Only upper jaw teeth row count and difference in the size of spines on the mid-rear wings differentiated the two species. Also, for both species, the proportion of dorsal fins joined, disc shape and relative tail length changed with total length. Secondary reproductive anatomy, clasper length and vas deferens weight, shell gland and uterus weight underwent initial acceleration in growth when the gonads transitioned to stage 2 (adolescent, maturing). Also, YOY A. hyperborea were found to distribute at shallower depths than larger stages, constituting a nursery, which was not observed for A. jenseni. Full article
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44 pages, 26944 KiB  
Article
Description of a Remarkable New Skate Species of Leucoraja Malm, 1877 (Rajiformes, Rajidae) from the Southwestern Indian Ocean: Introducing 3D Modeling as an Innovative Tool for the Visualization of Clasper Characters
by Simon Weigmann, Matthias F. W. Stehmann, Bernard Séret and Hajime Ishihara
Biology 2024, 13(6), 405; https://doi.org/10.3390/biology13060405 - 2 Jun 2024
Cited by 1 | Viewed by 2731
Abstract
A remarkable new deep-water skate, Leucoraja longirostris n. sp., is described based on eight specimens caught during different expeditions to the southern Madagascar Ridge in the southwestern Indian Ocean. The new species differs from all congeners by its remarkably long and acutely angled [...] Read more.
A remarkable new deep-water skate, Leucoraja longirostris n. sp., is described based on eight specimens caught during different expeditions to the southern Madagascar Ridge in the southwestern Indian Ocean. The new species differs from all congeners by its remarkably long and acutely angled snout (horizontal preorbital length 17.2–22.6% TL vs. 8.5–11.9% TL and 4.2–6.1 vs. 1.7–3.5 times orbit length, snout angle 65–85° vs. 90–150°). Furthermore, it is apparently endemic to the Madagascar Ridge, distant from the known distribution areas of all congeners. In addition to L. fullonica and L. pristispina, L. longirostris n. sp. is also the only species with plain dorsal coloration. Furthermore, the new species is the only Leucoraja species with an external clasper component dike and, besides L. wallacei, the only one with four dorsal terminal (dt) cartilages. The shape of the accessory terminal 1 (at1) cartilage with four tips is also unique within the genus. A new approach for the visualization of the clasper characters is introduced based on 3D models of all skeletal and external features. This enables a much easier and much more precise interpretation of every single clasper component, of the entire structure, and, in particular, the relationship between external features and skeletal cartilages. A new English translation of the first diagnosis of Leucoraja is provided, along with a revised generic diagnosis and a key to the species of Leucoraja in the Indian Ocean. Full article
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22 pages, 10333 KiB  
Article
Additions to the Taxonomy of the Antarctic Dark-Mouth Skate Bathyraja arctowskii (Dollo, 1904), with Descriptions of the Syntypes and Morphology of Teeth, Dermal Denticles and Thorns
by Simon Weigmann and Thomas Reinecke
Diversity 2023, 15(8), 899; https://doi.org/10.3390/d15080899 - 30 Jul 2023
Cited by 2 | Viewed by 2275
Abstract
The taxonomy of the enigmatic dark-mouth skate, Bathyraja arctowskii (Dollo, 1904), from the Southern Ocean was finally resolved after more than 100 years of ambiguity in 2021. This species is the smallest known species of the species-rich deep-water skate genus Bathyraja Ishiyama, 1958, [...] Read more.
The taxonomy of the enigmatic dark-mouth skate, Bathyraja arctowskii (Dollo, 1904), from the Southern Ocean was finally resolved after more than 100 years of ambiguity in 2021. This species is the smallest known species of the species-rich deep-water skate genus Bathyraja Ishiyama, 1958, which attains a total length of only about 61 cm and appears to be a wide-ranging and locally common species in the Southern Ocean. It differs from its congeners in the small adult size, dark-pigmented mouth cavity and underside of nasal curtain, lack of thorns on upper disc, as well as small and slender egg cases. Although the identity of this species was unambiguously clarified, the syntype egg cases could not be examined due to the COVID-19 pandemic. This examination has now become possible, and detailed data of the syntypes are provided in the present paper for the first time, together with hitherto unknown details of tooth, dermal denticle and thorn morphology. Furthermore, a lectotype and two paralectotypes are designated from the syntypes. Full article
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21 pages, 2538 KiB  
Article
Gradients of Variation in the At-Vessel Mortality Rate between Twelve Species of Sharks and Skates Sampled through a Fishery-Independent Trawl Survey in the Asinara Gulf (NW Mediterranean Sea)
by Umberto Scacco, Tomaso Fortibuoni, Matteo Baini, Gianluca Franceschini, Dario Giani, Margherita Concato, Cristina Panti, Alessia Izzi and Michela Angiolillo
Biology 2023, 12(3), 363; https://doi.org/10.3390/biology12030363 - 24 Feb 2023
Cited by 3 | Viewed by 2868
Abstract
Elasmobranchs are priority species for conservation due to their rapid decline determined by the unbalanced struggle between a fragile bio-ecology and strong anthropogenic impacts, such as bycatch from professional fishing. In this context, measuring species resistance to catch of poorly selective gear is [...] Read more.
Elasmobranchs are priority species for conservation due to their rapid decline determined by the unbalanced struggle between a fragile bio-ecology and strong anthropogenic impacts, such as bycatch from professional fishing. In this context, measuring species resistance to catch of poorly selective gear is of paramount importance. During June–October 2022, five experimental fishing campaigns were carried out in the Asinara Gulf (northern Sardinia) through 35 geographically and bathymetrically representative hauls of an area between 30 and 600 m in depth. Skates prevailed over sharks in the number of species, with seven and five species, respectively. We first evaluated the status of each individual with respect to stress due to the trawl’s catch using a three-graded scale. We also recorded individual biometrics (total and disk length, weight and sex, and maturity for males) on board by implementing the best practices in manipulating individuals for physiological recovery and release at sea. After capture, skates resulted in generally better conditions than sharks, although deepwater species of both groups exhibited a worse state than coastal species. The estimated vitality rates also depended on the size of the individuals. This work provides standardized data on the intermingled effect of size, species type, and inhabited depth on the resistance response of some elasmobranch species against capture by trawl fishery activities. Full article
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28 pages, 10797 KiB  
Article
Long-Term Changes in the Distribution and Abundance of Nine Deep-Water Skates (Arhynchobatidae: Rajiformes: Chondrichthyes) in the Northwestern Pacific
by Alexei M. Orlov and Igor V. Volvenko
Animals 2022, 12(24), 3485; https://doi.org/10.3390/ani12243485 - 9 Dec 2022
Cited by 8 | Viewed by 1672
Abstract
Based on the analysis of long-term data from bottom trawl surveys (1977–2021), changes in the spatial distribution, position of the boundaries of the ranges and the catch rates of the nine most common deep-sea skates of the genus Bathyraja in the Russian waters [...] Read more.
Based on the analysis of long-term data from bottom trawl surveys (1977–2021), changes in the spatial distribution, position of the boundaries of the ranges and the catch rates of the nine most common deep-sea skates of the genus Bathyraja in the Russian waters of the Northwestern Pacific (B. violacea, B. aleutica, B. matsubarai, B. maculata, B. bergi, B. taranetzi, B. minispinosa, B. interrupta, and B. isotrachys) are considered. During the surveyed period, significant changes in the spatial distribution were observed, which are probably due to both subjective reasons (changes in the number of trawling stations, surveyed depths, etc.) and climatic changes. No monotonous displacement of the northern or southern boundaries of the range or its center in one direction was observed in any area of any species during the entire observation period. At the same time, shifts in the boundaries of the ranges of different species in different areas occurred for different decades, i.e., the boundaries of the ranges slowly fluctuated or “pulsed” near some average annual position. In general, from the 1970s to the 1980s, the number of skates grew; from the 1980s to the 1990s, it decreased; from the 1990s to the 2000s, it fluctuated at the achieved level; from the 2000s to the 2010s, it grew again; and from the 2010s to the 2020s, it decreased again. These trends coincide with previously identified ecosystem rearrangements under the influence of climatic and oceanological changes. The identification of links between changes in spatial distribution, range boundaries and catch rates with climatic and oceanological factors require separate additional studies. Full article
(This article belongs to the Special Issue Sharks and Skates: Ecology, Distribution and Conservation)
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26 pages, 1378 KiB  
Review
Taking Advantage of the Genomics Revolution for Monitoring and Conservation of Chondrichthyan Populations
by Shaili Johri, Michael P. Doane, Lauren Allen and Elizabeth A. Dinsdale
Diversity 2019, 11(4), 49; https://doi.org/10.3390/d11040049 - 29 Mar 2019
Cited by 22 | Viewed by 8313
Abstract
Chondrichthyes (sharks, rays, skates and chimaeras) are among the oldest extant predators and are vital to top-down regulation of oceanic ecosystems. They are an ecologically diverse group occupying a wide range of habitats and are thus, exploited by coastal, pelagic and deep-water fishing [...] Read more.
Chondrichthyes (sharks, rays, skates and chimaeras) are among the oldest extant predators and are vital to top-down regulation of oceanic ecosystems. They are an ecologically diverse group occupying a wide range of habitats and are thus, exploited by coastal, pelagic and deep-water fishing industries. Chondrichthyes are among the most data deficient vertebrate species groups making design and implementation of regulatory and conservation measures challenging. High-throughput sequencing technologies have significantly propelled ecological investigations and understanding of marine and terrestrial species’ populations, but there remains a paucity of NGS based research on chondrichthyan populations. We present a brief review of current methods to access genomic and metagenomic data from Chondrichthyes and discuss applications of these datasets to increase our understanding of chondrichthyan taxonomy, evolution, ecology and population structures. Last, we consider opportunities and challenges offered by genomic studies for conservation and management of chondrichthyan populations. Full article
(This article belongs to the Special Issue Review Papers on Marine Diversity)
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