Thorny Skate Research Articles

Development of a technological solution aimed at improving the consumer properties of a new fish culinary product enriched with chondroitin sulfate of thorny skate

The paper presents the results of developing a fish culinary product (thorny skate meat mixed with Atlantic cod meat, baked with potatoes and mushrooms in a cream sauce) enriched with chondroitin sulfate contained in the meat and cartilage of the wings of thorny skate. Atlantic cod, more familiar to the Russian consumer and successfully complementing the skate's meat with amino acid composition, has been chosen as an additional fish raw material. Thorny skate belongs to the underutilized fishing facilities of the Northern Basin. The meat of its wings contains up to 1.5 % urea, which worsens its organoleptic properties. To solve this problem, it was previously proposed to use short-term preliminary heat treatment (PHT) of skate's wings by blanching them in water at a temperature from 93 to 96 °C for 1–3 minutes, which guarantees a fourfold decrease in the mass fraction of urea in the meat, relative to the initial content, below the organoleptic perception of the consumer. PHT also facilitates the cutting of the skate's meat. The formulation and technology of a combined fish culinary product is proposed, packaged and completely ready for consumer's use. To prolong the shelf life up to 120 days, it is proposed to subject the product to shock freezing with subsequent storage at a temperature no higher than minus 18 °C. To solve the problem of delamination of cream sauce during storage and to improve the consumer properties of the product, an experimentally based technological solution is proposed – the introduction of oat flour in the composition of the sauce formulation as a thickener and structure-forming agent in an amount of 3.5 % per total mass of sauce.

Mitogenomic evidence of population differentiation of thorny skate, Amblyraja radiata, in the North Atlantic.

Management of thorny skate (Amblyraja radiata) in the Northwest Atlantic has posed a conservation dilemma for several decades due to the species' lack of response to strong conservation efforts in the US Gulf of Maine and the Canadian Scotian Shelf, confusion over the relationship between two reproductive size morphs of differing life histories that are sympatric in the Northwest Atlantic, and conflicting data on regional population connectivity throughout the species' broader range. To better assess potential A. radiata regional population differentiation and genetic links to life-history variation, we analysed complete mitochondrial genome sequences from 527 specimens collected across the species' North Atlantic geographic range, with particular emphasis on the Northwest Atlantic region. A high level of genetic diversity was evident across the North Atlantic, but significant genetic differentiation was identified between specimens inhabiting the Northwest (Gulf of Maine and Newfoundland) and Northeast (Greenland, Iceland, North Sea, and Arctic Circle) Atlantic. In the Northwest Atlantic, significant differentiation between the Gulf of Maine and Newfoundland regions was revealed; however, the overall level of differentiation was very low. No genetic difference was identified between the large and small reproductive morphs. The results of this study advance our understanding of A. radiata population structure in the North Atlantic but do not resolve all the questions confounding our understanding of the species' biology and evolutionary history.

Species independence of eye lens dimensions in teleosts and elasmobranchs.

The vertebrate eye lens grows incrementally, adding layers of elongated, tightly packed lens fiber cells at the outer margin of the lens. With subsequent growth, previously-deposited fiber cells degrade, leaving a region of fully denucleated and organelle-free cells which are responsible for the high transparency and low light scattering characteristics of the lens. The objective of this study was to determine if the horizon separating the gelatinous outer cortex of the lens from its hardened interior occurred at a consistent location within the lens of several teleost and elasmobranch fish species, and could be linked to fiber cell morphology or function. A fixed ratio of 0.69±0.01 of hardened eye lens diameter (HD) to overall eye lens diameter (LD) was observed in a broad size range of Atlantic cod (Gadus morhua), haddock (Melanogrammus aeglefinus), thorny skate (Amblyraja radiata) and round ray (Rajella fyllae). The location of the hardened lens horizon was similar to that reported for optical plasticity and spherical aberration, but not that of fiber cell denucleation, suggesting that fiber cell dehydration continues after the loss of internal organelles. Our findings support a previous suggestion that the maintenance of optical quality during fish eye lens growth requires a precisely-fixed HD:LD ratio, while the ubiquity of a fixed ratio across fish taxa may suggest that many fish species possess a common refractive index profile. The linear relationship between HD and fish length should allow fish length to be backcalculated from the diameter of the isolated lens core, thus aiding research using isotope ratios of lens laminae or inner cores to reconstruct early life history events.

Contemporary analyses of comparative fishing data: a case study of Thorny skate on the Grand Banks (NAFO Divisions 3LNOP)

We re-analyze Thorny skate data from two comparative fishing experiments conducted by DFO in 1995 and 1996 using improved and more contemporary methods to estimate the relative efficiency of the Campelen 1800 demersal shrimp trawl survey protocol compared to the Engel 145 otter trawl. We correct possible bias in the method previously applied to these data. We investigate if there are size-based differences and if depth or spatial regions have important effects on results. We also investigate the influence and robustness of the estimation procedures, which was a concern in the original analyses of these data for other groundfish species. We did not find strong evidence that the relative efficiency of the Campelen trawl protocol compared to the Engel was different for smaller-sized Thorny skate compared to larger ones. However, we conclude that there is a potential that size-based differential catchability existed but there is insufficient information to reliably estimate these effects for Thorny skate. We also found evidence of significant differences in relative efficiency among NAFO Divisions and experiments, which is similar to other flatfish species. However, the mechanisms for these differences are unknown and it is not clear if spatial estimates should be used when converting Engel indices to Campelen equivalents. Hence, we do not recommend a different Engel-Campelen conversion factor than the one currently used in stock assessments for Thorny skates on the Grand Banks (NAFO Divisions 3LNOPs).

Improving the effectiveness of preliminary heat treatment (blanching) of cartilage fish of the Northern Basin

Blanching is the process of preliminary heat treatment (PHT) of raw materials or semi-finished products before canning using various methods, which serves to inactivate unfavorable enzymes, improve organoleptic properties of the product produced and increase its storage period. Modern trend to rationalization of raw material processing requires the search for new methods of more efficient use of natural resources. Existing traditional blanching technology is well developed, but has a number of significant drawbacks. The article presents the methodology of experimental research focused on combined blanching, delivers the overview results of the most rational temperature of pre-heat treatment (combined blanching - water-steam), the effect of the steam generator capacity on the loss of raw materials mass and PHT is assessed. The article analyzes the advantages and disadvantages of blanching with water and steam separately. The use of both methods in one technological process made it possible to mitigate the disadvantages of each method individually. While improving the method of combined blanching, a mathematical model was obtained, allowing to perform the prediction calculation of rational modes of PHT of thorny skate, to produce a product with the necessary final characteristics. Based on the results of improving the method of combined blanching, with sequential use of water and steam, a continuous PHT tunnel-type unit was designed. It was decided to issue the patent on this utility model. The use of combined methods allows reducing the impact of disadvantages of each method applied. The technology of using combined blanching will make it possible to process the underutilized water biological resources of the northern seas, broaden the product range and reduce the price of the product for the consumer.

Contemporary analyses of comparative fishing data: a case study of Thorny skate on the Grand Banks (NAFO Divisions 3LNOP)

We re-analyze Thorny skate data from two comparative fishing experiments conducted by DFO in 1995 and 1996 using improved and more contemporary methods to estimate the relative efficiency of the Campelen 1800 demersal shrimp trawl survey protocol compared to the Engel 145 otter trawl. We correct possible bias in the method previously applied to these data. We investigate if there are size-based differences and if depth or spatial regions have important effects on results. We also investigate the influence and robustness of the estimation procedures, which was a concern in the original analyses of these data for other groundfish species. We did not find strong evidence that the relative efficiency of the Campelen trawl protocol compared to the Engel was different for smaller-sized Thorny skate compared to larger ones. However, we conclude that there is a potential that size-based differential catchability existed but there is insufficient information to reliably estimate these effects for Thorny skate. We also found evidence of significant differences in relative efficiency among NAFO Divisions and experiments, which is similar to other flatfish species. However, the mechanisms for these differences are unknown and it is not clear if spatial estimates should be used when converting Engel indices to Campelen equivalents. Hence, we do not recommend a different Engel-Campelen conversion factor than the one currently used in stock assessments for Thorny skates on the Grand Banks (NAFO Divisions 3LNOPs).

The Evolution of Oxytocin and Vasotocin Receptor Genes in Jawed Vertebrates: A Clear Case for Gene Duplications Through Ancestral Whole-Genome Duplications.

The neuronal and neuroendocrine peptides oxytocin (OT) and vasotocin (VT), including vasopressins, have six cognate receptors encoded by six receptor subtype genes in jawed vertebrates. The peptides elicit a broad range of responses that are specifically mediated by the receptor subtypes including neuronal functions regulating behavior and hormonal actions on reproduction and water/electrolyte balance. Previously, we have demonstrated that these six receptor subtype genes, which we designated VTR1A, VTR1B, OTR, VTR2A, VTR2B and VTR2C, arose from a syntenic ancestral gene pair, one VTR1/OTR ancestor and one VTR2 ancestor, through the early vertebrate whole-genome duplications (WGD) called 1R and 2R. This was supported by both phylogenetic and chromosomal conserved synteny data. More recently, other studies have focused on confounding factors, such as the OTR/VTR orthologs in cyclostomes, to question this scenario for the origin of the OTR/VTR gene family; proposing instead less parsimonious interpretations involving only one WGD followed by complex series of chromosomal or segmental duplications. Here, we have updated the phylogeny of the OTR/VTR gene family, including a larger number of vertebrate species, and revisited seven representative neighboring gene families from our previous conserved synteny analyses, adding chromosomal information from newer high-coverage genome assemblies from species that occupy key phylogenetic positions: the polypteriform fish reedfish (Erpetoichthys calabaricus), the cartilaginous fish thorny skate (Amblyraja radiata) and a more recent high-quality assembly of the Western clawed frog (Xenopus tropicalis) genome. Our analyses once again add strong support for four-fold symmetry, i.e., chromosome quadruplication in the same time window as the WGD events early in vertebrate evolution, prior to the jawed vertebrate radiation. Thus, the evolution of the OTR/VTR gene family can be most parsimoniously explained by two WGD events giving rise to the six ancestral genes, followed by differential gene losses of VTR2 genes in different lineages. We also argue for more coherence and clarity in the nomenclature of OT/VT receptors, based on the most parsimonious scenario.

Technology of Quick-Frozen Flour Fish Culinary Products

In this article, the results of the development of the functional fish culinary product “Thorny Skate and Cod Pie” are presented. A traditional recipe was used for making the yeast dough for the pie. The pie filling recipe was designed using Fuzzy Logic in the Matlab software package.Optimized parametersfor the selected sensory evaluation of the pie were calculated. On the basis of a priori information, key components of the filling (including the fraction of the fish components and skate meat) were chosen as the factors of interest. According to the simulation results, the optimal values werea 50/50 percentage for the first and the second factor respectively, and this providedthe maximum organoleptic assessment (five points on a five-point scale). The simulation results were compared with the results of the organoleptic evaluation of the pie made according to the optimized recipe, and their sufficient convergence was shown. The indicators of mass fraction of amine nitrogen and nitrogen of volatile bases was studied, as well as the microbiological safety indicators of flour fish culinary products, in accordance with the requirements of the Technical Regulations of the Eurasian Economic Union 040/2016 ”On the safety of fish products”. The results showed a high efficiency of the shock freezing of the semi-finished product, brought to semi-readiness, for long-term storage (120 days at a temperature no higher than minus 18 ∘C), without reducing the quality or safety of the pie. The product had a cholesterol content from 220 to 260 mg%, which allowed it to be classified as functional. The nutritional values of the product (mass fraction of protein, fat, carbohydrates, and amino acid composition) are presented.
 Keywords: thornyskate, functional product, pie with thornyskate and cod, shock freezing

Phenotypic regionalization of the vertebral column in the thorny skate Amblyraja radiata: Stability and variation.

Regionalization of the vertebral column occurred early during vertebrate evolution and has been extensively investigated in mammals. However, less data are available on vertebral regions of crown gnathostomes. This is particularly true for batoids (skates, sawfishes, guitarfishes, and rays) whose vertebral column has long been considered to be composed of the same two regions as in teleost fishes despite the presence of a synarcual. However, the numerous vertebral units in chondrichthyans may display a more complex regionalization pattern than previously assumed and the intraspecific variation of such pattern deserves a thorough investigation. In this study, we use micro-computed tomography (µCT) scans of vertebral columns of a growth series of thorny skates Amblyraja radiata to provide the first fine-scale morphological description of vertebral units in a batoids species. We further investigate axial regionalization using a replicable clustering analysis on presence/absence of vertebral elements to decipher the regionalization of the vertebral column of A. radiata. We identify four vertebral regions in this species. The two anteriormost regions, named synarcual and thoracic, may undergo strong developmental or functional constraints because they display stable patterns of shapes and numbers of vertebral units across all growth stages. The third region, named hemal transitional, is characterized by high inter-individual morphological variation and displays a transition between the monospondylous (one centrum per somite) to diplospondylous (two centra per somite) conditions. The posteriormost region, named caudal, is subdivided into three sub-regions with shapes changing gradually along the anteroposterior axis. These regionalized patterns are discussed in light of ecological habits of skates.

Пищевая и биологическая ценность функциональных фаршевых консервов из ската звездчатого (Amblyraja radiate)

The paper presents the results of a study of indicators that characterize the nutritional and biological value of new functional products-canned minced thorny skate with the addition of Atlantic cod – «Meatballs of stingray and cod in tomato sauce» and «Thorny skate and cod in white sauce». The content of 100 g of the product of the main food nutrients, namely, protein – from 8.4 to 10.0 g, fat – from 2.6 to 6.7 g, carbohydrates – from 10.2 to 18.1 g, depending on the recipe, was experimentally established. Studies have confirmed the high content of minor food substance – chondroitin sulfate (CS) – in canned thorny skate from 250 to 270 mg per 100 g of the product, which provides the recommended level of adequate consumption from 35.7 to 38.6%. On the basis of experimental data on the amino acid composition of the protein of new products, the indicators characterizing the biological value are calculated. Based on the results of the study, a reasonable conclusion was made about the high nutritional value and the presence of functional properties in canned thorny skate with the addition of Atlantic cod.

HapSolo: an optimization approach for removing secondary haplotigs during diploid genome assembly and scaffolding

BackgroundDespite marked recent improvements in long-read sequencing technology, the assembly of diploid genomes remains a difficult task. A major obstacle is distinguishing between alternative contigs that represent highly heterozygous regions. If primary and secondary contigs are not properly identified, the primary assembly will overrepresent both the size and complexity of the genome, which complicates downstream analysis such as scaffolding.ResultsHere we illustrate a new method, which we call HapSolo, that identifies secondary contigs and defines a primary assembly based on multiple pairwise contig alignment metrics. HapSolo evaluates candidate primary assemblies using BUSCO scores and then distinguishes among candidate assemblies using a cost function. The cost function can be defined by the user but by default considers the number of missing, duplicated and single BUSCO genes within the assembly. HapSolo performs hill climbing to minimize cost over thousands of candidate assemblies. We illustrate the performance of HapSolo on genome data from three species: the Chardonnay grape (Vitis vinifera), with a genome of 490 Mb, a mosquito (Anopheles funestus; 200 Mb) and the Thorny Skate (Amblyraja radiata; 2650 Mb).ConclusionsHapSolo rapidly identified candidate assemblies that yield improvements in assembly metrics, including decreased genome size and improved N50 scores. Contig N50 scores improved by 35%, 9% and 9% for Chardonnay, mosquito and the thorny skate, respectively, relative to unreduced primary assemblies. The benefits of HapSolo were amplified by down-stream analyses, which we illustrated by scaffolding with Hi-C data. We found, for example, that prior to the application of HapSolo, only 52% of the Chardonnay genome was captured in the largest 19 scaffolds, corresponding to the number of chromosomes. After the application of HapSolo, this value increased to ~ 84%. The improvements for the mosquito’s largest three scaffolds, representing the number of chromosomes, were from 61 to 86%, and the improvement was even more pronounced for thorny skate. We compared the scaffolding results to assemblies that were based on PurgeDups for identifying secondary contigs, with generally superior results for HapSolo.

Distributions of threatened skates and commercial fisheries inform conservation hotspots

Bycatch in commercial fisheries is a pressing conservation concern and has spurred global interest in adopting ecosystem-based management practices. To address such concerns, a thorough understanding of spatiotemporal relationships among bycatch species, their environment and fisheries is required. Here we used a generalized linear mixed model framework incorporating spatiotemporal random effects to model abundance patterns for 3 skate species caught as bycatch in commercial fisheries (thorny skate Amblyraja radiata, winter skate Leucoraja ocellata and smooth skate Malacoraja senta), as well as 10 target species on the Scotian Shelf, NW Atlantic. Spatiotemporal estimates of relative abundance for at-risk skates within the years 2005-2015 were modelled from research trawl survey data and overlaid with those for target species to identify hotspots of bycatch risk. In addition, abundance estimates for at-risk skates within the years 1975-1985, a period of higher stock abundance, were used to identify areas of previously important habitat. Historically, skate species densely occupied areas near Sable Island and Banquereau Banks, Georges Bank and the Bay of Fundy. Bycatch hotspots between at-risk skates and commercial targets were identified in regions across the Scotian Shelf. These hotspots were independently validated by predicting species presence from at-sea observer data that monitor skate bycatch directly. We discuss spatial relationships between target and bycatch species, highlighting limitations of at-sea observer programmes that this method helps to address. This framework can be applied more broadly to inform ecosystem management and priority areas for conservation or fisheries regulation.

Parasitic flatworms infecting thorny skate, Amblyraja radiata: Infection by the monogeneans Acanthocotyle verrilli and Rajonchocotyle emarginata in Svalbard.

Parasite diversity above the Arctic circle remains understudied even for commercially valuable host taxa. Thorny skate, Amblyraja radiata, is a common bycatch species with a growing commercial value. Its natural range covers both sides of the North Atlantic including the Arctic zone. Svalbard is a Norwegian archipelago located on the northwest corner of the Barents Shelf which sustains a spectacular species diversity. So far, several monogenean species have been reported infecting thorny skate across the Atlantic Ocean. In the present study, we intend to fill in the knowledge gap on monogenean parasites infecting thorny skate in the northern part of its range and thus indirectly assess the connectivity between the thorny skate populations off the Svalbard coast and from previously studied locations. 46 monogenean individuals were recovered from 11 specimens of thorny skate. Following morphological and molecular assessment, two species of monogeneans, Acanthocotyle verrilli and Rajonchocotyle emarginata, were identified. The results serve as the northernmost record for both parasite genera and the first record of monogenean species off Svalbard. Detailed morphometric evaluation revealed a relatively high level of morphological variation in A. verrilli compared to its congeners. Phylogenetic reconstruction placed A. verrilli in a well-supported clade with A. imo. Our study also suggests high diagnostic significance of sclerotised structures in the identification of Rajonchocotyle. Even though the occurrence of two directly transmitted parasite species supports the previously suggested long-distance migration of A. radiata, future studies employing highly variable genetic markers are needed to assess the ongoing and historical migration patterns.

Modeling the impacts of climate change on thorny skate (Amblyraja radiata) on the Northeast US shelf using trawl and longline surveys

AbstractClimate change has been shown to impact marine fish populations and communities. With small population sizes, long reproduction times, and a rapidly warming habitat, thorny skate (Amblyraja radiata) could be particularly vulnerable. To examine this possibility, we used a two‐stage generalized additive model to project future thorny skate abundances under two different climate scenarios. This is the first study in the northeastern United States to compare projections based on different survey methods (bottom trawl and longline), and results were heavily impacted by survey methodology. Models trained with the NOAA Bottom Trawl Survey projected a decrease in abundance of ~60%–80% in the Gulf of Maine and Georges Bank under the RCP 8.5 climate scenario. With aggressive mitigation (RCP 4.5), these decreases could be reduced to ~35%–45%. Models trained with a recent NOAA longline survey indicated that thorny skate abundance would be reduced 22% and 37% under business as usual and mitigation, respectively. There are substantial methodological differences between the two data sets, including capture technique and efficiency, total habitat coverage, and spatio‐temporal coverage. This underscores the importance of continued, methodologically diverse surveys on the Northeast US continental shelf. Our results indicate that climate change will continue to negatively impact thorny skate populations by reducing the amount of thermally suitable habitat in the southern extent of their range. This information should be considered in future management decisions.

Using conventional and pop-up satellite transmitting tags to assess the horizontal movements and habitat use of thorny skate (Amblyraja radiata) in the Gulf of Maine

AbstractThorny skate (Amblyraja radiata) have experienced decreasing abundance and range contraction in the Gulf of Maine (GOM) in recent decades. To better understand the extent to which population structure, environmental conditions, and movement ecology may play a role in these disruptions, 128 “mark-report” pop-up satellite tags (mrPATs) and 2195 conventional tags were deployed from 2002 to 2019. Data obtained from 84 mrPATs and 43 conventional tag recaptures [127 individuals: 55 males, 72 females; 32–104 cm total length (TL)] revealed minimum linear horizontal movements of 0.4–46.8 km in all cardinal directions over periods 22–3435 d. There was no relationship between days at liberty, TL, sex, depth, reporting season, or tag type and minimum linear displacement, and no broad seasonal movements were evident. Skates were observed at depths 27–201 m and in water temperatures 2.5–12.5°C, with fluctuations in both depth and temperature evident by season. Given their restricted movements, thorny skate may represent a single stock/population with metapopulation-like structure in the GOM. The pervasiveness of sedentary behaviour may also place the species at risk of localized depletion and climate change but also demonstrates the potential efficacy of spatial closures for promoting population recovery.

Study of rheological properties of gels based on Thorny Skate cartilage broth (<i>Raja radiata</i>) in the technology of natural fish culinary products -aspic fish, in jelly, fish jellies and potions

The paper deals with methodological approaches to study the rheological properties of gelatin gels based on the thorny skate cartilage broth ( Raja radiate ), which is an aqueous extract of chondroitin sulfate, depending on the manufacturing technology. It is shown that the use of modern instrumental methods for studying the rheological properties of gels and methodological approaches typical of physical and colloidal chemistry allows to obtain the most complete and objective information about the mechanisms of formation of key consumer properties of fish products and the main directions of improving the technology of its manufacture. The influence of gelatin concentration in the range from 0.5 to 5.0 % in chondroitin sulfate-containing broths from the thorny skate cartilage on kinematic and dynamic viscosity of broths, as well as on the strength, melting point and shear stress indices of gels based on these broths was studied. As control samples, aqueous solutions of gelatin in concentrations from 0.5 to 5.0 % and gels based on them were used in the studies. The analysis of the results of the study showed that the broths prepared on the basis of the thorny skate cartilage have increased relative to the control samples the values of kinematic and dynamic viscosity, the increase in indicators is characterized by a directly proportional dependence on the concentration of gelatin in the broth. Gelatin gels based on chondroitin sulfate-containing broths made from the thorny skate cartilage have increased strength, which has a positive effect on the organoleptic evaluation and consumer properties of the finished culinary products.

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).

Technology of Minced Fish Canned Food from Thorny Skate, Enriched with Chondroitin Sulfate

The article presents the results of theoretical and experimental research on the development of technology of functional minced fish canned food. Study of consumer preferences and the market of canned fish in the Murmansk region allowed to determine the range of novelties such as canned fish (”Skate and cod in white sauce” and ”Meatballs made from skate and cod in tomato sauce”), enriched with chondroitin sulfate (CS). The use of thorny skate’s (a fish that lives in the North Atlantic and the Barents Sea) wings meat for canning purposes enriches the composition of canned food. The content of CS in one can of canned food with net weight of 250 g ranged from 550 to 700 mg. This guarantees the intake of human body from 78 to 100% of the daily rate of this powerful chondroprotector. To remove urea from the skate’s meat, the method of infrared blanching is proposed, which ensures the efficiency in removal of urea at over 70% of its initial content in fish. Infrared blanching allows not only saving raw materials from unpleasant smell, but also partially removing water from it (water losses are from 8 to 13%). Partial dehydration of raw materials allows avoiding formation of water sedimentation in ready-made canned goods after sterilization. With the help of the fuzzy logic method, the MatLab program determines the optimal formulations of canned food, which guarantee their best consumer properties. The Ellab device has been used to experimentally select sterilization modes, which guarantee industrial sterility of canned food, hence the actual sterilization effect is higher than the standard one. During the two years of research, experimental studies of organoleptic properties, microbiological and biochemical changes in canned food were carried out, which made it possible to establish the shelf life: one year at a storage temperature not exceeding 20ºC.

Morphology and evolutionary significance of phosphatic otoliths within the inner ears of cartilaginous fishes (Chondrichthyes)

BackgroundChondrichthyans represent a monophyletic group of crown group gnathostomes and are central to our understanding of vertebrate evolution. Like all vertebrates, cartilaginous fishes evolved concretions of material within their inner ears to aid with equilibrium and balance detection. Up to now, these materials have been identified as calcium carbonate-bearing otoconia, which are small bio-crystals consisting of an inorganic mineral and a protein, or otoconial masses (aggregations of otoconia bound by an organic matrix), being significantly different in morphology compared to the singular, polycrystalline otolith structures of bony fishes, which are solidified bio-crystals forming stony masses. Reinvestigation of the morphological and chemical properties of these chondrichthyan otoconia revises our understanding of otolith composition and has implications on the evolution of these characters in both the gnathostome crown group, and cartilaginous fishes in particular.ResultsDissections of Amblyraja radiata, Potamotrygon leopoldi, and Scyliorhinus canicula revealed three pairs of singular polycrystalline otolith structures with a well-defined morphology within their inner ears, as observed in bony fishes. IR spectroscopy identified the material to be composed of carbonate/collagen-bearing apatite in all taxa. These findings contradict previous hypotheses suggesting these otoconial structures were composed of calcium carbonate in chondrichthyans. A phylogenetic mapping using 37 chondrichthyan taxa further showed that the acquisition of phosphatic otolith structures might be widespread within cartilaginous fishes.ConclusionsDifferences in the size and shape of otoliths between taxa indicate a taxonomic signal within elasmobranchs. Otoliths made of carbonate/collagen-bearing apatite are reported for the first time in chondrichthyans. The intrinsic pathways to form singular, polycrystalline otoliths may represent the plesiomorphic condition for vertebrates but needs further testing. Likewise, the phosphatic composition of otoliths in early vertebrates such as cyclostomes and elasmobranchs is probably closely related to the lack of bony tissue in these groups, supporting a close relationship between skeletal tissue mineralization patterns and chemical otolith composition, underlined by physiological constraints.

Modeling the distribution of thorny skate (Amblyraja radiata) in the southern Grand Banks (Newfoundland, Canada)

Globally, commercial fisheries have had a strong impact on elasmobranch populations directly through high catch rates and indirectly through bycatch. Consequently, the abundance of many species is declining to the extent that some are considered under threat of extinction. Regionally, this negative trend is also evident in the international waters of the southern Grand Banks (off the coast of Newfoundland, Canada), where the occurrence of the thorny skate (Amblyraja radiata) has declined by nearly 70% in recent decades. This study used Bayesian species distribution models to investigate the habitat preference and biomass trends of the thorny skate during a 14-year period (2003–2017), linking five environmental predictors (i.e., bathymetry, sea bottom temperature, seabed aspect, slope, and rugosity) and prey distribution with fishery-independent data. Our findings identify some of the sensitive habitats for this species and the ecological factors that may be driving its population dynamics in the area. We argue that knowledge about the factors influencing the distribution of this species and spatiotemporal effects could be exploited as potential mitigation measures for future fishery management strategies.