Deania Calcea Research Articles

Diet of Two Deep-Water Sharks, Deania calcea (Lowe, 1839) and Deania profundorum (Smith and Radcliffe, 1912), in the North Atlantic of Morocco

Diet of Two Deep-Water Sharks, Deania calcea (Lowe, 1839) and Deania profundorum (Smith and Radcliffe, 1912), in the North Atlantic of Morocco

A glimpse into the trophic ecology of deep-water sharks in an important crustacean fishing ground.

Deep-water sharks are among the most vulnerable deep-water taxa because of their extremely conservative life-history strategies (i.e., late maturation, slow growth, and reproductive rates), yet little is known about their biology and ecology. Thus, this study aimed at investigating the trophic ecology of five deep-water shark species, the birdbeak dogfish (Deania calcea), the arrowhead (D. profundorum), the smooth lanternshark (Etmopterus pusillus), the blackmouth catshark (Galeus melastomus) and the knifetooth dogfish (Scymnodon ringens) sampled onboard a crustacean bottom-trawler off the south-west coast of Portugal. We combined carbon and nitrogen stable isotopes with RNA and DNA (RD) ratios to investigate the main groups of prey assimilated by these species and their nutritional condition, respectively. Stable isotopes revealed overall small interspecific variability in the contribution of different taxonomic groups to sharks' tissues, as well as in the origin of their prey. S. ringens presented higher δ15 N and δ13 C values than the other species, suggesting reliance on bathyal cephalopods, crustaceans and teleosts; the remaining species likely assimilated bathy-mesopelagic prey. The RD ratios indicated that most of the individuals had an overall adequate nutritional condition and had recently eaten. This information, combined with the fact that stable isotopes indicate that sharks assimilated prey from the local or nearby food webs (including commercially important shrimps), suggests a potential overlap between this fishing area and their foraging grounds, which requires further attention.

Observations of sperm storage in some deep-sea elasmobranchs

The presence of sperm storage was evaluated in several deep-sea elasmobranchs (Centrophorus squamosus, Centroselachus crepidater, Deania calcea, Brochiraja spinifera, Brochiraja asperula, Apristurus ampliceps, A. exsanguis, A. garricki and A. sinensis), all considered at risk to the impacts of fishing in New Zealand. Biological measurements of reproductive organs (e.g. follicle size and number, oviducal gland size, uterus width and gonad weight) were recorded in addition to conventional macroscopic maturity assessment measures. Histology was conducted on a sample of oviducal glands to investigate the occurrence of sperm storage. Sperm storage was confirmed in three of the nine species: Centroselachus crepidater, Centrophorus squamosus and Brochiraja asperula. To the best of our knowledge, these are the first observations of sperm storage for these genera, and the first in the family Centrophoridae. Sperm storage was observed in macroscopically mature females and also in some females considered macroscopically as maturing. The female reproductive tract may regress substantially between reproductive events to the extent that a mature fish is mis-classified as maturing, and would be consistent with long periods of resting between reproductive events. Alternatively, it is equally possible that aggrieve male mating behaviour results in premature copulation of maturing females. We summarise published occurrences of sperm storage in chondrichthyans, and conclude that sperm storage is most likely ubiquitous in chondrichthyans, and an adaptive benefit to traumatic mating behaviour, that may also be adaptive to low fish densities in the relatively unproductive environment of the deep-sea.

Hg and Se composition in demersal deep-sea fish from the North-East Atlantic.

It has been emphasized that seafood consumers may have a higher risk of mercury (Hg) exposure. Nevertheless, the co-occurrence of selenium (Se) in organisms may affect the toxicity and bioavailability of Hg. In this work, we aim to demonstrate the possible role of Se as a potential protective element against Hg in muscle and liver tissues of three demersal deep-sea fish species: common mora Mora moro, birdbeak dogfish Deania calcea, and smooth lanternshark Etmopterus pusillus. Comparing species, the birdbeak dogfish D. calcea showed the highest Hg concentrations, the lowest Se levels, the lowest mean Se:Hg molar ratio, a negative HBV-Se index, and no correlation between total length. On the other hand, smooth lanternshark E. pusillus showed the lowest Hg concentrations, the highest Se concentrations, the highest mean Se:Hg molar ratio, a positive HBV-Se index, and a significant positive correlation between total length and Se concentrations in muscle. Comparing tissues, the common mora Mora moro seems to accumulate more Hg and Se in liver than shark species D. calcea and E. pusillus that showed to accumulate Hg and Se preferentially in muscle. Our results indicate that these three species for having Hg concentrations near and above the EU regulatory thresholds and for presenting low Se:Hg ratios, and negative (or low positive) HBV-Se index may pose a real risk of Hg toxicity for the consumer.

Taxonomic research on Deania calcea and Deania profundorum (Family: Centrophoridae) in the Cantabrian Sea (Northeast Atlantic) with comments on Deania hystricosa

Three elasmobranch species of the genus Deania are currently reported in NE Atlantic waters: D. calcea, D. hystricosa and D. profundorum; however, in north Spanish waters (NE Atlantic), only D. calcea and D. profundorum have been caught. Among the criteria used to discriminate Deania species one is dermal denticle length and body colour. In this study the authors explore the feasibility of these criteria and examine other morphological characters to investigate if sexual or ontogenic features had relevance for the distinction of the species particularly those sampled in this study, D. calcea and D. profundorum. Molecular analyses were conducted to validate these results.In D. calcea, dermal denticle length ranged from 340μm to 1400μm (763.2μm± 180.4 s.d.); in D. profundorum, dermal denticle length ranged from 195μm to 650μm (372.3μm± 111.7 s.d.). In both Deania species, a significant positive correlation was found between shark total length and dermal denticle length. Dermal denticles varied in size and shape along the shark body. These differences were significant both intra- and inter-specifically.A multivariate analysis based on morphological characters was used to test differences between D. calcea and D. profundorum. The hierarchical analysis clearly identified three groups; two groups corresponded to each species, and a third group discriminated between small and large individuals of D. profundorum. The morphometric characters that contributed most to the divergence between both species were mainly related to the size of the dorsal fins, the inter-dorsal distance and the distances from the snout to the origin of each dorsal fin. Based on morphological characters, no sexual dimorphism was observed.The phylogenetic tree was reconstructed with molecular COI sequences available on BOLD and those obtained in this study. The output tree discriminate D. calcea from D. profundorum, however could not separate molecularly D. calcea and D. hystricosa.

Elasmobranch species richness, fisheries, abundance and size composition in the Azores archipelago (NE Atlantic)

ABSTRACTElasmobranchs are a vulnerable resource, more susceptible to overfishing than most teleosts, and their assessment is complicated due to a general lack of information about their fisheries, biology and ecology. This study aimed to analyse all fishery and survey data available for elasmobranchs caught over the past c. 25 years around the Azores (NE Atlantic) to provide a baseline information, which can be used to inform stock assessment and management strategies. Elasmobranch species covered pelagic, benthopelagic and demersal habitats, from shallow to deep-water strata in areas around the islands and seamounts. These species are taken accidentally as by-catch of three main fisheries: swordfish fishery, black scabbardfish fishery and demersal bottom longline fishery. The latter represents one of the most important fishing activities in the Azores, and frequent elasmobranch by-catches include Raja clavata, Galeorhinus galeus, Deania calcea, D. profundorum, Etmopterus pusillus and E. spinax. A slight reduction in the abundance indices of these species was observed, despite the implemented technical measures (e.g. minimum size, zero catch). Little is known about resource dynamics for the Azorean region and no analytical assessments have been conducted. This study highlights the vulnerability to overfishing of these resources and the urgent need to develop management strategies.

Near-equal compressibility of liver oil and seawater minimises buoyancy changes in deep-sea sharks and chimaeras.

Whereas upper ocean pelagic sharks are negatively buoyant and must swim continuously to generate lift from their fins, deep-sea sharks float or swim slowly buoyed up by large volumes of low-density oils in their livers. Investigation of the pressure, volume, temperature (PVT) relationships for liver oils of 10 species of deep-sea Chondrichthyes shows that the density difference between oil and seawater, Δρ, remains almost constant with pressure down to full ocean depth (11 km, 1100 bar), theoretically providing buoyancy far beyond the maximum depth of occurrence (3700 m) of sharks. However, Δρ does change significantly with temperature and we show that the combined effects of pressure and temperature can decrease buoyancy of oil by up to 10% between the surface and 3500 m depth across interfaces between warm southern and cold polar waters in the Rockall Trough in the NE Atlantic. This increases drag more than 10-fold compared with neutral buoyancy during horizontal slow swimming (0.1 m s-1), but the effect becomes negligible at high speeds. Chondrichthyes generally experience positive buoyancy change during ascent and negative buoyancy change during descent, but contrary effects can occur at interfaces between waters of different densities. During normal vertical migrations buoyancy changes are small, increasing slow-speed drag no more than 2- to 3-fold. Equations and tables of density, pressure and temperature are provided for squalene and liver oils of Chimaeriformes (Harriotta raleighana, Chimaera monstrosa, Hydrolagus affinis), Squaliformes (Centrophorus squamosus, Deania calcea, Centroscymnus coelolepis, Centroscyllium fabricii, Etmopterus spinax) and Carcharhiniformes (Apristurus laurussonii, Galeus murinus).

A Serravallian (Middle Miocene) shark fauna from Southeastern Spain and its palaeoenvironment significance

The study of a new Serravallian (Middle Miocene) locality from the Southeastern Spain has yielded a shark assemblage characterized by microremains of at least seven taxa (Deania calcea, †Isistius triangulus, †Squaliolus cf. S. schaubi, †Paraetmopterus sp., Pristiophorus sp., Scyliorhinus sp. and a cf. Squaliformes indet) of three different orders (Squaliformes, Pristiophoriformes and Carcharhiniformes). In addition, associated macroremains have also been found, including teeth of †Cosmopolitodus hastalis, Isurus sp., Hemipristis serra, Odontaspis sp., Carcharhinus spp. and †Otodus (Megaselachus) megalodon. The assemblage contains taxa with disparate environmental preferences including not only neritic and epipelagic sharks but also an important number of meso and bathypelagic representatives. The migration of deep water taxa to shallower waters through submarine canyons/coastal upwelling is proposed as the most plausible cause for explaining the origin of such assemblage. Interestingly, the composition of the deep-water taxa here reported contrast with the chondrichthyans assemblages from the Pliocene and extant Mediterranean communities. This entails a complex biogeographic history, where the Messinian salinity crisis strongly affected the posterior evolution of the Mediterranean ecosystems but some other factors, such us the existence of anoxic events during the Quaternary, could have also played an important role.

The diversity, distribution and status of deep-water elasmobranchs in the Rockall Trough, north-east Atlantic Ocean.

Data from a scientific deep-water trawl fisheries survey in the north-east Atlantic were analysed to determine the spatial and bathymetric distribution of elasmobranch species and assess the change in relative abundance over the period 1998-2013. During this period, commercial fisheries for deep-water sharks went from being entirely unregulated, to being briefly managed, to being completely prohibited. A total of 22 species of shark and 10 species of skate were recorded between depths of 300 and 2030 m. All showed strong species-specific depth-related trends in abundance. Out of the 11 more common species, five showed no change in relative abundance over time, two (Centrophorus squamosus and Centroselachus crepidater) declined significantly and four increased in relative abundance (Apristurus aphyodes, Apristurus microps, Galeus melastomus and Deania calcea). Assuming these populations were depleted by fisheries in the past, the current data do not suggest there has been an overall recovery. Positive signs for some species in the most recent years suggest movement or recruitment back into the area; however, it is of concern that two species continued to decline. There is a continued need to have precautionary management of these elasmobranch species, and the current ban on landing these species in European waters remains appropriate.

Trophic relationships of hake (Merluccius capensis and M. paradoxus) and sharks (Centrophorus squamosus, Deania calcea and D. profundorum) in the Northern (Namibia) Benguela Current region

The trophic relationships of two hake species (Merluccius capensis and M. paradoxus) and three shark species (Centrophorus squamosus, Deania calcea and D. profundorum) were investigated using nitrogen and carbon stable isotope signatures (δ15N and δ13C) of their muscle tissues. The sharks were more enriched in 15N than the hake, an indication of the apex predator status of sharks. Among the sharks considered, C. squamosus occupied the highest trophic level and fed primarily on benthic prey. The two species of shark from the genus Deania were not different based on δ15N or δ13C, so they had similar diets. The δ13C signatures indicated that M. capensis and sharks fed on prey derived from similar basal resources. However, there was a significant difference in δ13C between M. paradoxus and all other species examined, suggesting that they occupied different feeding niches. Isotope-based population metrics showed narrower trophic ranges in sharks than M. capensis. Carbon and nitrogen ranges indicated that hake fed on a more diverse pool of carbon sources and had generally more enhanced trophic diversity in their feeding patterns than sharks. Among the species considered, C. squamosus occupied a unique isotopic space. Our results supported the hypothesis there are trophic overlaps among these species, but some interesting differentiation was revealed.

Geographical variability in life-history traits of a midslope dogfish: the brier shark Deania calcea.

Deania calcea (n = 420) were collected from the catch of deep-water trawlers in the southern and eastern scalefish and shark fishery in southern Australia during the years 2008-2011. The total length (LT ) range varied between sexes, females being larger (n = 264; 280-1530 mm) than males (n = 156; 310-921 mm). The reproductive cycle in this population is non-continuous and asynchronous. The estimated LT at which 50% of males are mature is 807 mm and is 914 mm for females. Populations of D. calcea in higher latitudes appear to mature at a larger size than conspecifics in lower latitudes, in both the northern and southern hemispheres. Litters ranged from three to 10 embryos with a 1:1 sex ratio, but litter size does not increase with maternal LT . Deania calcea shows geographical variability in its biological parameters and gathering information on life-history traits of populations is vital to understand the trade-offs made by this species in response to environmental conditions and to predict intraspecific spatial differences. Such information is a basis for specific spatial management to protect populations from excessive fishing.

Composition of glycosaminoglycans in elasmobranchs including several deep-sea sharks: identification of chondroitin/dermatan sulfate from the dried fins of Isurus oxyrinchus and Prionace glauca.

Shark fin, used as a food, is a rich source of glycosaminoglyans (GAGs), acidic polysaccharides having important biological activities, suggesting their nutraceutical and pharmaceutical application. A comprehensive survey of GAGs derived from the fin was performed on 11 elasmobranchs, including several deep sea sharks. Chondroitin sulfate (CS) and hyaluronic acid (HA) were found in Isurus oxyrinchus, Prionace glauca, Scyliorhinus torazame, Deania calcea, Chlamydoselachus anguineus, Mitsukurina owatoni, Mustelus griseus and Dasyatis akajei, respectively. CS was only found from Chimaera phantasma, Dalatias licha, and Odontaspis ferox, respectively. Characteristic disaccharide units of most of the CS were comprised of C- and D-type units. Interestingly, substantial amount of CS/dermatan sulfate (DS) was found in the dried fin (without skin and cartilage) of Isurus oxyrinchus and Prionace glauca. 1H-NMR analysis showed that the composition of glucuronic acid (GlcA) and iduronic acid (IdoA) in shark CS/DS was 41.2% and 58.8% (Isurus oxyrinchus), 36.1% and 63.9% (Prionace glauca), respectively. Furthermore, a substantial proportion of this CS/DS consisted of E-, B- and D-type units. Shark CS/DS stimulated neurite outgrowth of hippocampal neurons at a similar level as DS derived from invertebrate species. Midkine and pleiotrophin interact strongly with CS/DS from Isurus oxyrinchus and Prionace glauca, affording Kd values of 1.07 nM, 6.25 nM and 1.70 nM, 1.88 nM, respectively. These results strongly suggest that the IdoA-rich domain of CS/DS is required for neurite outgrowth activity. A detailed examination of oligosaccharide residues, produced by chondroitinase ACII digestion, suggested that the IdoA and B-type units as well as A- and C-type units were found in clusters in shark CS/DS. In addition, it was discovered that the contents of B-type units in these IdoA-rich domain increased in a length dependent manner, while C- and D-type units were located particularly in the immediate vicinity of the IdoA-rich domain.

Barcoding deep-water chondrichthyans from mainland Portugal

Most deep-water chondrichthyans occurring off mainland Portugal are distributed worldwide. There are many closely related species with similar morphology, and the lack of diagnostic characters that unambiguously allow species discrimination has led to extensive identification problems. Here, DNA barcodes were used to evaluate the suitability of cytochrome c oxidase I (COI) to identify deep-water chondrichthyans and to further contribute to the worldwide molecular databases currently in use. The sample was composed of 40 individuals from the families Chimaeridae, Centrophoridae, Somniosidae, Etmopteridae, Oxynotidae, Dalatiidae, Scyliorhinidae, Mitsukurinidae, Chlamydoselachidae and Hexanchidae. COI proved to be adequate for species identification, with almost all putative species recovered as well supported monophyletic clades, with low intraspecific variation. Sequence matches against the BOLD database provided evidence for the existence of identification problems particularly within the genera Hydrolagus, Galeus and Centrophorus. Present results suggest that three different Centrophorus species occur off the Portuguese mainland, C. squamosus, C. granulosus and C. uyato. The sample also included an albino Deania calcea and a C. squamosus specimen without dermal denticles. This study updates the current knowledge on diversity and distribution of deep-water chondrichthyans occurring along the Portuguese coast, and provides an essential tool for species identification and consistency of taxonomic designations worldwide.

Large-scale distribution of three deep-water squaloid sharks: Integrating data on sex, maturity and environment

Deep-water sharks exhibit species-specific reproductive strategies, which include segregation by sex, size and reproductive stage. However, due to the wide spatial distribution of most species, available information, usually collected at a regional scale, is usually not adequate to infer species reproductive spatial dynamics. This study draws together information on the distribution of reproductive stages of three species of squaliform sharks: Portuguese dogfish Centroscymnus coelolepis (Somniosidae), leafscale gulper shark Centrophorus squamosus (Centrophoridae) and birdbeak dogfish Deania calcea (Centrophoridae), gathering data from several geographical areas from the Atlantic, Indian and Pacific Oceans. For each species we analysed the sex ratio and the spatial patterns of reproductive stages within regions, considering the influence of geographical area, depth, season, temperature and salinity. The combination of statistical methods used in this study successfully identified a number of life history patterns which reflect different use of habitats by sex and life cycle stage. Pregnant females of the three species are spatially segregated, inhabiting shallower and/or warmer waters. In the case of the leafscale gulper shark this segregation might be associated with large scale migrations. In contrast, in Portuguese dogfish all adult maturity stages occur in the same geographical area. Pregnant female birdbeak dogfish were rare in all samples. Larger immature specimens of all the three species distribute deeper than the remaining maturity stages in most of the regions analysed. Mature males of leafscale gulper shark and birdbeak dogfish were more broadly distributed than mature females, supporting the possibility of sex-biased dispersal. Neonates and small sized specimens were scarce in the Northeast Atlantic potentially explained by their concentration in nurseries, and/or by gear selectivity. Management measures will benefit from considering the geographic scale of demographic variation between species. However, standardized collaborative approaches will be needed for comprehensive assessment.

Trophic Interactions and Distribution of Some Squaliforme Sharks, Including New Diet Descriptions for Deania calcea and Squalus acanthias

Squaliforme sharks are a common but relatively vulnerable bycatch in many deep water fisheries. Eleven species of squaliforme shark are commonly caught at depths of 200–1200 m on Chatham Rise, New Zealand, and their diversity suggests they might occupy different niches. The diets of 133 Deania calcea and 295 Squalus acanthias were determined from examination of stomach contents. The diet of D. calcea was characterised by mesopelagic fishes, and S. acanthias by benthic to pelagic fishes, but was more adaptive and included likely scavenging. Multivariate analyses found the most important predictors of diet variability in S. acanthias were year, bottom temperature, longitude, and fish weight. The diet of the nine other commonly caught squaliforme sharks was reviewed, and the spatial and depth distribution of all species on Chatham Rise described from research bottom trawl survey catches. The eleven species had a variety of different diets, and depth and location preferences, consistent with niche separation to reduce interspecific competition. Four trophic groups were identified, characterised by: mesopelagic fishes and invertebrates (Centroselachus crepidater, D. calcea, and Etmopterus lucifer); mesopelagic and benthopelagic fishes and invertebrates (Centroscymnus owstoni, Etmopterus baxteri); demersal and benthic fishes (Centrophorus squamosus, Dalatias licha, Proscymnodon plunketi); and a generalist diet of fishes and invertebrates (S. acanthias). The trophic levels of the species in each of the four groups were estimated as 4.18–4.24, 4.20–4.23, 4.24–4.48, and 3.84 respectively. The diet of Oxynotus bruniensis and Squalus griffini are unknown. The different niches occupied by different species are likely to influence their vulnerability to bottom trawl fisheries. Some species may benefit from fisheries through an increased availability of scavenged prey.

Risks and benefits' consumption of birdbeak dogfish Deania calcea

PurposeThere are very few studies that characterize the properties of the edible part from deep‐water fish species which constitute a new target for developing fisheries. Therefore this paper aimed to examine the balance between health benefits and risks associated to the birdbeak dogfish consumption, with a special emphasis on the assessment of the risks of toxic metal intake.Design/methodology/approachBetween September 2008 and May 2009, 82 individuals were analysed. The chemical composition (moisture, ash, protein and lipid content), essential elements (zinc (Zn), copper (Cu), iron (Fe), potassium (K), magnesium (Mg) and sodium (Na)), toxic elements (mercury (Hg), cadmium (Cd) and lead (Pb)) and fatty acid composition were determined using standard procedures.FindingsThe species is a lean fish (fat content <2.0 per cent) and for both females and males the mineral concentration in descending order was K>Na>Mg>Fe>Zn>Cu. The edible part of birdbeak dogfish is a good source of several minerals, namely K and Na, reaching respectively ca 18 and 36 per cent of the recommended daily intakes for a 150 g muscle portion. Polyunsaturated fatty acids prevail in the fatty acid composition of both sexes and significant differences between females and males were only found in palmitic acid, arachidonic acid and omega 6. Females attained larger length and higher Hg values. The risk assessment was established for three different consumption scenarios (one and two portions of 150 g per month and one portion of 150 g per week) and showed that only a regular consumption of one portion of a female dogfish per week posed a higher health risk (15 per cent).Practical implicationsThis study presents the information about the quantity of shark muscle (in g) to be ingested in terms of the PTWI allowing each consumer to have access to the risks and benefits in eating this fish.Originality/valueNo data existed for fatty acid profile and risk assessment yet and this is the first information on the essential and toxic elements for the European waters.

Reproductive strategy of the female deep-water shark birdbeak dogfish,Deania calcea: lecithotrophy or matrotrophy?

Little information is available on the maternal–embryonic relationships among sharks. Birdbeak dogfish (Deania calcea) has been described as ovoviviparous, but this term comprises a wide range of forms on how the embryos are nourished including lecithotrophy and matrotrophy. To evaluate the maternal–embryonic relationship in birdbeak dogfish we have analysed chemical features (fatty acid composition and mercury (Hg) levels) and biological characteristics (egg and embryo dry weight variation, uterus characterization). Monounsaturated fatty acids were the dominant fatty acids in eggs while polyunsaturated fatty acids (PUFA) were the dominant fatty acids in both pregnant females and embryos. Significant differences were found among eggs, embryos and pregnant females for all fatty acids groups with the exception of saturated fatty acids for embryos and pregnant females. The principal components analysis revealed that embryos are particularly related to n-6 PUFA and pregnant females with n-3 PUFA. A close relationship exists between the Hg level of pregnant females and the Hg level of their embryos which indicates that there is a transfer of mercury from maternal sources. The comparison of the mean dry weight between eggs and embryos showed a gain of 3.8% obtained in the embryos. Histological sections of the uteri of pregnant females showed a high level of both superficial and inner vascularization in the uterine villi as well as the presence of secretor cells. Until now, the importance of this species maternal contribution and interference for the embryos development has never been documented. However, the biological and chemical results observed in the present work show that there is a matrotrophic strategy for the birdbeak dogfish.

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.

Determination of the total lipid and the long chain omega-3 polyunsaturated fatty acids, EPA and DHA, in deep-sea fish and shark species from the North-East Atlantic

The lipid and long chain omega-3 polyunsaturated fatty acid (LC ω-3 PUFA) contents of spot samples of 22 under-utilised species of deep-sea fish were determined. The total lipid content was determined by a rapid extraction technique which used anhydrous sodium sulphate and ethanol to immobilise the moisture in the fish tissue followed by extraction of lipid with hep-tane at 80-85°C. The heptane extract was analysed in a liquid cell between NaCl windows on an infra-red (IR) spectrophotometer. Lipid content of the extract was calculated from the area of the IR spectrophotometric ester stretching band between 1700 and 1800cm-1. After evapora-tion of the heptane, the residue was determined gravimetically. The IR and gravimetric (where sufficient crude lipid quantities were present) results were generally in good agreement. Eigh-teen fish had lipid contents 1.1g/100g, ranging from 0.18 (birdbeak dogfish, Deania calceus) to 1.1g/100g (forkbeard, Phycis blennoides), while four had lipid contents ranging from 4.25 (Baird’s smoothead, Alepocephalus bairdii) to 16.2g/100g (snake mackerel, Nessiarchus nas-sutus). However, both snake mackerel and orange roughy (Hoplostethus atlanticus) produced IR spectra consistent with the literature findings that they contain high levels of undigestible wax esters. The ω-3 PUFA, eicosapentaenoic acid (C20:5ω-3, EPA) and docosahexaenoic acid (C22:6ω-3, DHA) were determined using capillary gas chromatography. As a source of dietary ω-3 PUFA, the low-fat fish were generally poor suppliers with amounts ranging from 0.04g/100g (birdbeak dogfish) to 0.29g/100g (greater argentine, Argentina silus) but several species were not substantially inferior to cod (Gadus morhua). The tw high lipid species containing large amounts of wax esters, although having appreciable levels of ω-3 PUFA would not be desirable from a dietary point of view. In most of the fish DHA was present at 3 to 6 times the level of EPA.

Resource utilization by deep‐sea sharks at the Le Danois Bank, Cantabrian Sea, north‐east Atlantic Ocean

The feeding habits of birdbeak dogfish Deania calcea, velvet belly lantern shark Etmopterus spinax and blackmouth catshark Galeus melastomus at Le Danois Bank, Cantabrian Sea, south Bay of Biscay were studied in relation to their bathymetric distribution. Deep-sea sharks were collected during two multidisciplinary surveys carried out in October 2003 and April 2004 at the Le Danois Bank. Two different habitats were defined: (1) the top of the bank, ranging from 454 to 642 m depth and covered by fine-sand sediments with a low percentage of organic matter, and (2) the inner basin located between the bank and the Cantabrian Sea's continental shelf, at depths of 810-1048 m, which was characterized by a high proportion of silt and organic matter. Deania calcea was not present at the top of the bank but was abundant below 642 m, while E. spinax was abundant in the shallower top of the bank but was not found in the deeper inner basin. There was almost no bathymetric overlap between these two deep-sea shark species. Galeus melastomus was found over the whole depth range. There seemed to be an ontogenetic segregation with depth for this species, however, since 80% of the specimens collected at the top of the bank were < 600 mm total length (L(T)) (mean 510 mm L(T)), whereas larger individuals (mean 620 mm L(T)) inhabited deeper zones. Galeus melastomus exhibited a significantly higher feeding intensity than both E. spinax at the top of the bank and D. calcea in the inner basin. Little dietary overlap between D. calcea and G. melastomus in the inner basin was found, with D. calcea being an ichthyophagous predator while the diet of G. melastomus at these depths was composed of a variety of meso-bathypelagic shrimps (e.g. Acantephyra pelagica, Pasiphaea spp. and Sergia robusta), cephalopods and fishes. The diets of E. spinax and G. melastomus at the top of the bank showed a high dietary overlap of euphausiids, which represented the main prey taxa for both species. Euphausiids declined in abundance with depth which was reflected in the diet of G. melastomus. The cluster analysis of prey affinities among hauls depicted two major groups, corresponding to the two different habitats (top of the bank and inner basin). Redundancy analysis also indicated top-basin segregation, with euphausiids representing the main prey taxa at the top of the bank and bathypelagic shrimps in the inner basin. Euphausiids and Micromesistius poutassou were key prey within the Le Danois Bank ecosystem since they were positively selected by the three deep-sea shark species. These results show that the feeding ecology of these predators in Le Danois Bank ecosystem is highly influenced by depth-related variables, as a result of changes in prey availability. Overall results were analysed in relation to the deep-sea Le Danois ecosystem structure and functioning.