Amblyraja Hyperborea Research Articles

Sibling Species Amblyraja hyperborea and A. jenseni in Slope Waters of Eastern Canada: An Ecomorphological Description

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.

Seamount coral reefs are egg case nurseries for deep-sea skates.

Egg case nurseries of the boreal skate (Amblyraja hyperborea) and Richardson's skate (Bathyraja richardsoni) were defined and mapped on a bathyal seascape (~500-1,900 m depths) south of Tasmania, Australia, using 99 towed-camera transects (157 linear km; N= 50,858 images). In total, 738 skate egg cases were observed (present in 240 images, absent in 50,618); among 113 egg cases examined to identify parent species, 70% were A. hyperborea, 10% B. richardsoni and 20% unidentified Bathyraja species. 'Recently laid' egg cases were differentiated from 'aged' by classifying their colour and condition. The great majority (98%) of egg cases were observed in ~1,100-1,400 m depths on seamounts (15 of 36 surveyed), not seamount bases or adjacent continental slope. Egg cases were associated with reefs formed by accumulated skeletal matrix of the stony coral Solenosmilia variabilis, with >90% egg cases (including most of those recently laid) observed on living S. variabilis that characterises a 'coral zone' in ~950-1,350 m depths. Water in the coral zone is warmer (+0.66 to 2.37°C) than at the deep distributional limits of adult A. hyperborea and B. richardsoni (2,000 and 3,000 m, respectively), potentially providing for accelerated embryonic development. Co-occurrence with living coral infers an energetically favourable local-scale hydrodynamic environment for egg cases, particularly on seamount peaks, where increased water flow over egg cases would avert smothering by suspended sediment, and compensate for lower oxygen concentration compared to deeper depths occupied by adult skates. Criteria identifying egg case nurseries are strongly met for A. hyperborea at Seamount Z110 (468 egg cases of varied ages, maximum density of 5.47 m-2 ) and to a lesser extent on five others (Seamounts K1, Z16, Hill U, Z5 and Hill V). An abundance (density) criterion for defining nurseries needs to be flexible because it is a spatially scale-dependent measure that differs between surveys according to the tools and design employed. Off Australia, coral reef egg case nursery habitat is restricted to a narrow depth range in temperate latitudes where it is scarce and impacted by historical bottom trawl fishing in many locations. There has been effective conservation of nursery habitat, however, because four of the six nursery sites identified here and extensive coral reef areas are protected within marine parks. This article is protected by copyright. All rights reserved.

Combining telemetry and fisheries data to quantify species overlap and evaluate bycatch mitigation strategies in an emergent Canadian Arctic fishery

Greenland halibut Reinhardtius hippoglossoides are bottom-dwelling flatfish that support commercial and community fisheries in Baffin Bay, Canada. Recently, exploratory inshore summer fisheries have raised concerns surrounding the bycatch of Greenland sharks Somniosus microcephalus and Arctic skate Amblyraja hyperborea, which are susceptible to overfishing due to their conservative life history traits. To explore fisheries selectivity and opportunities for bycatch mitigation, we combined pop-up satellite archival tags (PSATs) and fisheries data to assess habitat overlap and catch trends across these 3 species. PSAT data showed variable inter-specific overlap, with Greenland sharks primarily inhabiting depths <1000 m (725 ± 193 m), Greenland halibut inhabiting a narrower depth range (1030 ± 113 m), and Arctic skates overlapping depths (950 ± 225 m) of both species. However, fisheries data suggested high inter-specific overlap at deepest depths, with peak catch-per-unit-effort (CPUE) of all species at depths 800-1000 m. A marked decline in Greenland shark CPUE was observed throughout the fishing season which was best explained by cumulative fishing pressure. Combined tagging and fisheries data suggest that targeting specific seasonal habitat will not decrease bycatch, and inshore summer longline fisheries should be evaluated in the context of potentially high elasmobranch mortality, with enforced bycatch handling practices and alternative mitigation measures (e.g. gear modification or reduced soak times) required.

Chemical and enzymatic destruction of chondroitin sulfate from Arctic skate

Due to its biocompatibility with human and animal tissues, low toxicity, and biodegradability, chondroitin sulfate (CS) is of great interest for medicine. Since CS is used as a pharmaceutical preparation, its molecular weight and solubility determine the possibilities of its use. This work presents the results of studying the chemical and enzymatic destruction of CS macromolecules and its effect on the molecular weight, solubility and crystallinity degree of the polysaccharide. CS was obtained from the cartilaginous tissue of the Arctic skate ( Amblyraja hyperborea ). At the stage of cartilage tissue fermentolysis, the enzymes pancreatin, hepatopancreatin and protosubtil were used. The obtained CS samples were identified by IR spectroscopy. Enzymatic destruction of glycosidic bonds in cholesterol macromolecules was carried out with a 1 % solution of the enzyme hepatopancreatin, chemical destruction with hydrogen peroxide and hydrochloric acid. The CS content in the samples was determined by the Dische method. The chemical composition of CS samples was evaluated by standard methods. The average molecular weight (MW) was determined using high performance liquid chromatography and the nephelometric method. The crystallinity degree (CD) was determined by graphical processing of diffraction patterns obtained by X-ray phase analysis of CS samples. It was found that under the action of hepatopancreatin and hydrogen peroxide, deep destruction of chondroitin sulfate occurs, to the formation of low molecular weight and oligomeric fragments. Under conditions of acid destruction in 0.5 N HCl for 20 min the MW of chondroitin sulfate is reduced by 10 % compared to the initial one. Acid destruction causes a significant decrease in the CD of the CS samples. For CS samples not degraded in acid, the solubility in distilled water increases with decreasing MW and CD. The solubility of CS after acid destruction in the range of pH = 5-9 units is 99.0 ± 0.5 %. This high solubility is most likely explained by the significant content of the amorphous phase in the samples.

Impacts of an Eruption on Cold-Seep Microbial and Faunal Dynamics at a Mud Volcano

Cold seeps are widespread in the deep sea and, like other chemosynthesis-based ecosystems, often host high faunal biomass. Temporal changes at seeps have been inferred by comparing communities at different successional stages; nonetheless, temporal studies in seep ecosystems are rare. Using data collected as part of a benthic observatory, we characterized intra-annual microbial and faunal dynamics in a microbial mat habitat on the Håkon Mosby mud volcano (1256 m depth; Barents Sea), and evaluated the effects of a mud eruption on the biota. Video sequences recorded twice daily for 4.5 months with an autonomous imaging module were analyzed to quantify changes in microbial mat cover and megafaunal density and behavior. In addition, time series data for pressure, bottom currents, and seabed temperature were analyzed to characterize environmental changes. Of the five taxa observed on the video footage, the zoarcid Lycodes squamiventer, the pycnogonid Nymphon macronyx, and the skate Amblyraja hyperborea were the most common. Zoarcids made frequent incursions on microbial mats, but were more often documented on the adjacent sediments. The cyclic behavior of common trends identified between microbial mat cover, zoarcid densities and abiotic variables using dynamic factor analysis (DFA) suggested that seep ecosystem dynamics at the Håkon Mosby mud volcano may be modulated by tides and the activity of the volcano. Moreover, the eruption that occurred about two months after the start of the study had a significant impact on faunal densities, microbial activity, and environmental variables. The eruption was preceded by a steady increase in seabed temperatures, density of small holes (indicative of gas emissions), and microbial mat cover. It was followed by 3- and 5-fold increase in zoarcid and pycnogonid densities, respectively. To our knowledge, this study is the first to analyze intra-annual temporal data in a cold-seep ecosystem and to present data on the effects of a mud eruption on seep microbial and faunal dynamics. Our results provide the first insight into ecosystem dynamics at a high-latitude cold seep and highlight the need to collect high-resolution temporal data to evaluate seep communities’ response to a warming Arctic and their potential role in mitigating methane emissions.

Characterization and phylogenetic analysis of the complete mitogenome of the Arctic skate Amblyraja hyperborea (Rajiformes; Rajidae)

The Arctic skate Amblyraja hyperborea is common in the cold water of the Atlantic and Pacific Arctic. Its distribution and taxonomy have been open to discussion. Here, we report on the whole mitochondrial genome sequence of A. hyperborea and the subsequent characterization. The mitogenome is 16,729 bp in length and consists of 13 protein-coding genes, 2 rRNA genes, and 22 tRNA genes. The phylogenetic tree we reconstruct with the mitogenomes of related skates within the order Rajiformes supports the monophyletic assemblage congruent with recent studies, whilst raising the necessity of further investigations to elucidate the relationship among some rajid genera.

Spatial patterns of arctic sponge ground fauna and demersal fish are detectable in autonomous underwater vehicle (AUV) imagery

Deep-sea sponge grounds are important habitats that provide several ecosystem services, yet relatively little is known about their distribution and ecology. While most surveys have focused on the broad-scale distribution patterns of sponge grounds (100s–1000s m), only rarely have the finer-scale (<10 m) spatial distribution patterns of the primary organisms been studied. In this study, the autonomous underwater vehicle (AUV) Hugin 1000 was used to map an area of an arctic sponge ground located on the summit of the Schulz Bank (Arctic Mid-Ocean Ridge), with the aim of detecting small-scale spatial patterns produced by the dominant megafauna. Using low-light cameras to construct a photomosaic comprising of 9,953 images and a virtual quadrat spatial sampling approach, density hotspots of the most prominent megafauna were visualized. The primary megafauna detected were demosponges, hexactinellids, ascidians, cnidarians, echinoderms, and demersal fish species. Most megafauna, like the primary structure-forming sponge species Geodia parva and Stelletta rhaphidiophora, were distributed evenly throughout the sample area, though species like Lissodendoryx (Lissodendoryx) complicata and Gersemia rubiformis displayed clear fine-scale spatial preferences. The three demersal fish species, Macrourus berglax, Reinhardtius hippoglossoides, and Amblyraja hyperborea, were uniformly distributed throughout the sample area. Based on the presence of skate egg cases and juveniles within many images, it is likely that the site is being used as a nursery ground for A. hyperborea. This study demonstrates the potential of using AUVs to detect fine-scale spatial patterns of the structure-forming sponges and demersal fish species. The use of AUVs for deep-water benthic surveys can help visualize how fauna (e.g. fish) utilise deep-sea habitats, and act as a tool for quantifying individuals through relatively unbiased means (e.g. pre-programmed track, no sampling). Such information is crucial for future conservation and management efforts.

In situ observations of deep-living skates in the eastern North Pacific

We report on 18 years of in situ observations of seven skate species (2192 individual observations) in the eastern North Pacific (Vancouver Island, Canada to the Gulf of California, Mexico) between 200 and 3322 m depth. Biological (species, sex, maturity, behavior) and abiotic (geographic location, depth, habitat type, temperature, oxygen) data were evaluated for each species. This study extends the depth and geographic ranges of Bathyraja microtrachys and B. trachura. Additional species studied include Amblyraja hyperborea, B. abyssicola, B. kincaidii, B. spinosissima, and Beringraja rhina. Bathyraja trachura was shown to be uniquely tolerant of low oxygen environments and B. spinosissima is distinctive in that it was most frequently found actively swimming over lava fields. Our video recording of a potentially undescribed species at 3321 m represents the deepest reported in situ visual observation of a skate to date.

Osmolyte Adjustments as a Pressure Adaptation in Deep-Sea Chondrichthyan Fishes: An Intraspecific Test in Arctic Skates (Amblyraja hyperborea) along a Depth Gradient.

Accumulation of trimethylamine N-oxide (TMAO) by deep-sea animals is proposed to protect proteins against the destabilizing effects of high hydrostatic pressure (the piezolyte hypothesis). Chondrichthyan fishes (sharks, rays, and chimaeras) provide a unique test of this hypothesis because shallow-living species have elevated TMAO levels to counteract the destabilizing effects of high urea levels accumulated for osmoregulation. Limited interspecific studies of chondrichthyans reveal that increasing depth correlates with decreased urea and increased TMAO levels, suggesting a dynamic balance between destabilizing forces on proteins (high urea, hydrostatic pressure) and TMAO to counteract these forces. Indeed, an inability to minimize urea levels or maximize TMAO levels has been proposed to explain why chondrichthyans are absent in the vast abyssal region. An unresolved question is whether the depth-related changes in chondrichthyan osmolytes are a flexible response to depth or whether phylogenetic differences in species-specific physiological set points for osmolytes account for the differences seen with depth. Sampling Arctic skates (Amblyraja hyperborea) across a 1,015-m depth gradient in the Beaufort Sea, we measured organic osmolytes in muscle using spectrophotometry and high-performance liquid chromatography. We found that the urea-to-TMAO ratio decreased linearly with depth, with tighter correlation than that seen in interspecific studies. Minor osmolytes, including betaine, sarcosine, and some α-amino acids, also declined with depth, apparently replaced (as with urea) by TMAO (a stronger piezolyte than those solutes). These data provide the first intraspecific evidence that flexible adjustments of osmolyte combinations are a key response for deep-sea living in individual chondrichthyans, supporting the piezolyte hypothesis.

Legacy and emergent POPs in the marine fauna of NE Greenland with special emphasis on the Greenland shark Somniosus microcephalus

Persistent organic pollutants include several groups of chemicals with similar structures and physical–chemical properties that elicit comparable toxic effects. They have been used extensively worldwide in agriculture, industrial, and health applications. Their degradation is very slow in the polar regions due to the low temperatures and winter darkness. The aims of this study were to determine the concentrations of polychlorobyphenils (PCBs), polybromodiphenylethers (PBDEs), perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA) in the Greenland sharks (Somniosus microcephalus) and other marine fishes and invertebrates from NE Greenland. The concentration increases were assessed by calculating the biomagnification factor (BMF) among pairs of alleged predator-prey organisms. PFOS were Careproctus reinhardti (5.02 ng/g wet wt) > stomach content of Amblyraja hyperborea (1.4454 ng/g wet wt) > Boreogadus saida (0.355 ng/g wet wt). The higher contaminant biomagnification was found in the predator → prey pairs: shark → invertebrates (BMF_Σ6PCBs = 75-88672, BMF_Σ3PBDEs = 14-124), shark → A. hyperborea → preys, according to their diets. Ecotoxicological baseline data on marine wildlife in NE Greenland are particularly important due to the risk of prospect petroleum activities.

Arctic skate Amblyraja hyperborea preys on remarkably large glacial eelpouts Lycodes frigidus.

During scientific surveys on the continental slopes north-west of Spitsbergen and off north-east Greenland (c. 600 and 1000 m depths), two female Arctic skates Amblyraja hyperborea were caught while swallowing extraordinary large individuals of glacial eelpout Lycodes frigidus. The total length (LT) of the prey constituted 50 and 80% of the LT of the skates, which reveal that A. hyperborea are capable predators of fishes of surprisingly large relative size.

Movement, depth and temperature preferences of an important bycatch species, Arctic skate Amblyraja hyperborea, in Cumberland Sound, Canadian Arctic

Climate change and increasing exploitation of resources are threats to Arctic marine species. Knowledge of vertical and horizontal movements of species is critical to understand their spatial ecology to inform effective ecosystem-based management. Recently, Arctic skate Am bly - raja hyperborea, a largely unstudied, cold water, deep-dwelling species has become a common bycatch species in groundfish fisheries throughout the Arctic. To investigate Arctic skate move- ment, depth and temperature preferences, 9 adults were tagged with pop-off archival transmitting tags in Cumberland Sound, Canadian Arctic, in August 2010 and August 2011 for 40 to 100 d. Of the 9 individuals tagged, 5 transmitted reliable data to satellites. Arctic skate occupied waters between 1.2 and 2.9°C (2.5 ± 0.1°C; mean ± SD) and 317 and 1355 m (944 ± 154 m). Tags popped off within a 37 km straight-line distance from the tagging location, indicating limited horizontal dispersal during the pre-ice formation period of late summer and early winter. Although mixed- effect models indicated that occupied depth varied with the diel cycle, the relationship was weak and depth variation was small, suggesting diel vertical migration does not appear to be a common strategy. Activity levels, estimated from detailed time series depth profiles, indicated multiple behaviours from resting to large depth changes (>150 m per 0.5 h). Given the levels of bycatch of this species in developing Arctic fisheries, overlap in habitat with the commercially valuable Greenland halibut Reinhardtius hippoglossoides and historical declines of skate populations, it is recommended that the IUCN Red List designation of 'Least Concern' for the Arctic skate be re-evaluated.

Persistence and Variation on the Groundfish Assemblages on the Southern Grand Banks (NAFO Divisions 3NO): 2002-2011

Data from EU-Spain (Instituto Espanol de Oceanografia) bottom trawl surveys in the NAFO Regulatory Area (2002–2011) were analyzed to examine patterns on the South of Grand Banks (NAFO Div. 3NO) of groundfish assemblage structure and diversity in relation to depth. The 1160 hauls from the slope surveys spanned between 38 and 1460 m in depth. We focused on the 28 most abundant species, which made up 92.6% of the catch in terms of biomass. Assemblage structure was strongly correlated with depth. For the most part, changes in assemblages seem to be fairly continuous, although there were more abrupt changes at 300 m. Five assemblages were identified. Two shallow assemblages were found in the shelf. Assemblage I (Shallow) comprises the strata with depths lesser than 150 and include yellowtail flounder (Limanda ferruginea), American plaice (Hippoglossoides platessoides), Northern sand lance (Ammodytes dubius), moustache sculpin (Triglops murrayi), capelin (Mallotus villosus) and web sculpin (Hemitripterus americanus). Assemblage II (Shallow) includes the strata with depths between 151 and 300 m and comprises Atlantic cod (Gadus morhua), American angler (Lophius americanus), wolfish (Anarichas lupus) and thorny skate (Amblyraja radiata). Assemblage III (Intermediate) contains the depth strata between 301 and 600 m. Redfish (Sebastes spp.), spotted wolfish (Anarichas minor), Arctic eelpout (Lycodes reticulatus), Northern wolfish (Anarichas denticulatus), white hake (Urophycis tenuis), witch flounder (Glyptocephalus cynoglossus) and longfin hake (Phycis chesteri) were included in the intermediate assemblage. Finally, we found two deep clusters: Assemblage IV (Deep) contains the depths between 601 and 1000 m, and Assemblage V (Deep) the depth strata greater than 1001 m. Greenland halibut (Reinhardtius hippoglossoides), marlin-spike (Nezumia bairdii), roughhead grenadier (Macrourus berglax) and spinytail skate (Bathyraja spinicauda) formed Assemblage IV. Snubnosed spiny eel (Notacanthus chemnitzii), blue antimora (Antimora rostrata), Northern cutthroat eel (Syphanobranchus kaupii), roundnose grenadier (Coryphaenoides rupestris), black dogfish (Centroscyllium fabricii), Arctic skate (Amblyraja hyperborea) and longnose chimera (Harriotta raleighana) made up the deepest assemblage. Despite dramatic changes in biomass and abundance of the species in the area, the boundaries and composition of the assemblages seem to be similar to the period before the collapse. Although some changes were evident, the main ones were replacements of the dominant species in several assemblages and bathymetric range extension of distribution of some species. Yellowtail flounder appears to be the dominant species in the shallowest assemblage instead of Atlantic cod and American plaice that were dominant in the period before the collapse in the area; redfish is the dominant species in the second shallow and intermediate assemblages. Diversity appears inversely related to biomass in the different assemblages. Despite the fishing effort in the deep waters of the Grand Banks, the overall pattern of demersal fish assemblages remains similar over time. This pattern is similar in other Atlantic areas; it indicates that changes in the fish populations in Northwest Atlantic have been produced on a large scale and are not limited to specific areas.

Trophic Transfer of Contaminants in a Changing Arctic Marine Food Web: Cumberland Sound, Nunavut, Canada

Contaminant dynamics in arctic marine food webs may be impacted by current climate-induced food web changes including increases in transient/subarctic species. We quantified food web organochlorine transfer in the Cumberland Sound (Nunavut, Canada) arctic marine food web in the presence of transient species using species-specific biomagnification factors (BMFs), trophic magnification factors (TMFs), and a multifactor model that included δ(15)N-derived trophic position and species habitat range (transient versus resident), and also considered δ(13)C-derived carbon source, thermoregulatory group, and season. Transient/subarctic species relative to residents had higher prey-to-predator BMFs of biomagnifying contaminants (1.4 to 62 for harp seal, Greenland shark, and narwhal versus 1.1 to 20 for ringed seal, arctic skate, and beluga whale, respectively). For contaminants that biomagnified in a transient-and-resident food web and a resident-only food web scenario, TMFs were higher in the former (2.3 to 10.1) versus the latter (1.7 to 4.0). Transient/subarctic species have higher tissue contaminant levels and greater BMFs likely due to higher energetic requirements associated with long-distance movements or consumption of more contaminated prey in regions outside of Cumberland Sound. These results demonstrate that, in addition to climate change-related long-range transport/deposition/revolatilization changes, increasing numbers of transient/subarctic animals may alter food web contaminant dynamics.

Preliminary structural characterization, anti-inflammatory and anticoagulant activities of chondroitin sulfates from marine fish cartilage

Chondroitin sulfates isolated from cartilage of five marine fish species: Atlantic salmon (Salmo salar), Greenland shark (Somniosus microcephalus), blackmouth catshark (Galeus melastomus), birdbeak dogfish (Deania calcea), and Arctic skate (Amblyraja hyperborea), were characterized in detail by 1H and 13C NMR spectroscopy. The complete signal assignments for carbohydrates were made and the relative contents of the key structural units were estimated by 2D homonuclear and heteronuclear NMR spectroscopy (COSY, TOCSY, NOESY, HSQC, and HMBC). The average length of the polysaccharide chain was evaluated from the integrated intensity ratio of the terminal and internal monosaccharide residues. The anti-inflammatory and anticoagulant activities of the specimens were studied. Chondroitin sulfates from salmon and Arctic skate exhibit considerable anti-inflammatory activity. All specimens manifest weak anticoagulant activity. The results of the present study indicate that chondroitin sulfates deserve more detailed investigation as potential anti-inflammatory agents.

Structure, function and molecular adaptations of haemoglobins of the polar cartilaginous fish Bathyraja eatonii and Raja hyperborea

Cartilaginous fish are very ancient organisms. In the Antarctic sea, the modern chondrichthyan genera are poorly represented, with only three species of sharks and eight species of skates; the paucity of chondrichthyans is probably an ecological consequence of unusual trophic or habitat conditions in the Southern Ocean. In the Arctic, there are 26 species belonging to the class Chondrichthyes. Fish in the two polar regions have been subjected to different regional histories that have influenced the development of diversity: Antarctic marine organisms are highly stenothermal, in response to stable water temperatures, whereas the Arctic communities are exposed to seasonal temperature variations. The structure and function of the oxygen-transport haem protein from the Antarctic skate Bathyraja eatonii and from the Arctic skate Raja hyperborea (both of the subclass Elasmobranchii, order Rajiformes, family Rajidae) is reported in the present paper. These species have a single major haemoglobin (Hb 1; over 80% of the total). The Bohr-proton and the organophosphate-binding sites are absent. Thus the haemoglobins of northern and southern polar skates appear functionally similar, whereas differences were observed with several temperate elasmobranchs. Such evidence suggests that, in temperate and polar habitats, physiological adaptations have evolved along distinct pathways, whereas, in this case, the effect of the differences characterizing the two polar environments is negligible.

By-catch of Skates in Trawl and Long-Line Fisheries in the Barents Sea

The occurrence of skates (Rajidae) in the by-catch of trawl and long-line fisheries in the Barents Sea are described. The dominant species captured were thorny skate or starry ray (Amblyraja radiate), arctic skate (A. hyperborea) and round skate (Rajella fyllae), whereas blue or big skate (Dipturus batis) and sail ray (D. linteus) were only caught occasionally. Information on the size distribution and sex ratio are provided. Larger skates were more often caught in long-line fisheries, with the mean and maximum length of fish greater in long-line catches, particularly for the larger-bodied species. Ratio of males to females was close to 1:1 in all species except for arctic skate where males dominated in the long-line fishery. Preliminary estimates of skate by-catch in these fisheries indicate that total annual by-catch of skate in the Barents Sea ranges from 723–1 891 tons. Thorny skate accounted for 90–95% of the total skate catch.

The Status of Skate Stocks in the Barents Sea

Annual trawl surveys conducted by Polar Research Institute of Marine Fisheries and Oceanography (PINRO) in the Barents Sea during 1998–2001 have been used to describe the distribution, habitat (temperature, salinity and depth), size distribution and sex ratio of six species of skates (thorny skate, Amblyraja radiata; Arctic skate, Amblyraja hyperborea; round skate, Rajella fyllae; blue skate, Dipturus batis; and spinytail skate, Bathyraja spinicauda). The relative biomass and abundance of the five species are presented.

Feeding and Food Consumption by the Barents Sea Skates

Stomach contents data were used to investigate spatial, seasonal and inter-annual patterns of feeding of the thorny skate (Amblyraja radiata) in the Barents Sea during 1994–2000. The diets and food consumption by the thorny skate of different size groups were analyzed and assessed with special reference to the consumption of commercial species of fishes and crustaceans. Less comprehensive data on food composition are presented for other less abundant Barents Sea skates: arctic skate (A. hyperborea), round skate (Rajella fyllae), blue skate (Dipturus batis), spinytail skate (Bathyraja spinicauda) and sail ray (D. linteus).

Observations on the Greenland Shark, Somniosus microcephalus, in Northern Baffin Island

Eighteen immature Greenland sharks (Somniosus microcephalus (Bloch and Schneider) 1801) were captured during the course of a study on the biology of the narwhal, Monodon monoceros. Most had been feeding on offal resulting from the whaling operation and on fish and seal meat discarded at the campsite. Other food consumed included two egg cases of the arctic skate, Raja hyperborea, previously unrecorded from this locality. Four narwhals and one white whale were attacked in the nets, the sharks removing large chunks of skin and blubber from the carcasses.