Alepocephalus Rostratus Research Articles

Biological features of nine deep-water fishes from the midslope of the Northwest African coast

The size distribution, sex ratio, spawning activity, and maturity of Alepocephalus bairdii, Alepocephalus productus, Alepocephalus rostratus, Bathygadus favosus, Bathygadus melanobranchus, Nezumia aequalis, Mora moro, Trachyscorpia echinata and Hoplostethus mediterraneus inhabiting the middle slope off Northwest Africa were analysed. Maturation takes place during the winter months, when a high proportion (>62%) of large individuals were observed in the mature, spawning or postspawning stage, with the exception of H. mediterraneus (57.3%). Negative allometric growth was recorded as a general pattern in both sexes, but isometric growth was recorded in females of A. productus, A. rostratus, and B. melanobranchus. Positive allometric growth was only observed in females of T. echinata. The length frequency distribution showed significant differences between sexes, except in A. productus and A. bairdii. Females of Macrouridae species were found to be larger and heavier than males. Sex ratios were generally unbalanced, but no bias was observed in N. aequalis, T. echinata, and H. mediterraneus. Relative size at sexual maturity ranged mainly between 0.66 and 0.72, but B. favosus, H. mediterraneus, and N. aequalis showed lower values (0.54–0.61). Sexual maturity is reached mainly at a size between 1 and 5 cm smaller in males than in females, except in A. bairdii and T. echinata.

The demersal bathyal fish assemblage of the Central-Western Mediterranean: Depth distribution, sexual maturation and reproduction

This study compiles information on the size distribution and reproductive patterns of five chondrichthyans and 10 bony species dwelling on the continental slope of the Central-Western Mediterranean (south-eastern Sardinian waters, depth 720–1890 m). The abundance of the relatively less numerous chondrichthyans was found to decrease with depth. Almost all chondrichthyan species had a long reproductive period throughout the year at all depths. In bony fishes, the upper bathymetric stratum (<1100 m) was dominated by species with continuous and seasonal (autumn-winter) spawning cycles. At intermediate and lower depths (>1100 m), continuous reproduction was the most common pattern. Both chondrichthyans and bony fishes exhibited large sizes at maturity and at first maturity (>75% and >60% of their maximum body length, respectively), supporting the hypothesis that most deep-sea fish populations are characterized by a delayed maturity, which makes them highly vulnerable to fishing pressure and over-exploitation. In some sharks, population partitioning was observed, according to life stage as a function of depth: adult/mature females occupied deeper habitats than males and juveniles. Conversely, Dipturus nidarosiensis female and male juveniles (>1100 m) were segregated from the adult/mature population, dwelling between 1000 and 1100 m. In four of the 10 bony fishes examined, we found a clear and significant predominance of females, particularly pronounced in Alepocephalus rostratus, which is clearly related to their K-reproductive strategy. The four key-selected species (Galeus melastomus, A. rostratus, Bathypterois mediterraneus and Trachyrincus scabrus), characterized by different reproductive strategies/modalities and feeding behaviours, were differently affected by depth and fluxes of organic matter (Particulate Organic Carbon concentration) from the photic zone towards the sea-bottom as a function of sex and life -stage.

An in vitro screening with emerging contaminants reveals inhibition of carboxylesterase activity in aquatic organisms

Pharmaceuticals and personal care products (PPCPs) form part of the new generation of pollutants present in many freshwater and marine ecosystems. Although environmental concentrations of these bioactive substances are low, they cause sublethal effects (e.g., enzyme inhibition) in non-target organisms. However, little is known on metabolism of PPCPs by non-mammal species. Herein, an in vitro enzyme trial was performed to explore sensitivity of carboxylesterase (CE) activity of aquatic organisms to fourteen PPCPs. The esterase activity was determined in the liver of Mediterranean freshwater fish (Barbus meridionalis and Squalius laietanus), coastal marine fish (Dicentrarchus labrax and Solea solea), middle-slope fish (Trachyrhynchus scabrus), deep-sea fish (Alepocephalus rostratus and Cataetix laticeps), and in the digestive gland of a decapod crustacean (Aristeus antennatus). Results showed that 100μM of the lipid regulators simvastatin and fenofibrate significantly inhibited (30–80% of controls) the CE activity of all target species. Among the personal care products, nonylphenol and triclosan were strong esterase inhibitors in most species (36–68% of controls). Comparison with literature data suggests that fish CE activity is as sensitive to inhibition by some PPCPs as that of mammals, although their basal activity levels are lower than in mammals. Pending further studies on the interaction between PPCPs and CE activity, we postulate that this enzyme may act as a molecular sink for certain PPCPs in a comparable way than that described for the organophosphorus pesticides.

Parasite communities of the deep-sea fish Alepocephalus rostratus Risso, 1820 in the Balearic Sea (NW Mediterranean) along the slope and relationships with enzymatic biomarkers and health indicators

This study examines the parasite communities of Alepocephalus rostratus and its influence on some fish biochemical markers and histological alterations. A. rostratus constitutes the second most important fish species, in terms of biomass, inhabiting the deep slope of the Catalan Sea (Balearic Sea, NW Mediterranean). The study revealed eight different parasite species in this host: one coccidian, one digenean, one monogenean, one cestode and four nematodes. The parasite fauna of A. rostratus was partially dominated by larval forms (four of the seven metazoan taxa found), which combined with low species richness corresponds to a parasite fauna pattern more typical of bathypelagic fish species rather than demersal ones. The larval tetraphyllideans and cucullanid nematodes were the predominant species. In relation to depth, differences in abundance of the nematodes Cucullaninae gen. sp. and Hysterothylacium aduncum were found, probably due to the dietary shift in the fish host at greater depth. Thus, Cucullaninae gen. sp. and H. aduncum could be regarded as indicators for discriminating populations of A. rostratus in relation to depth in NW Mediterranean waters. Of the biochemical markers examined, acetylcholinesterase (AChE) and lactate dehydrogenase (LDH) activities and lipid peroxidation (LP) levels, only LP showed significant differences between depths. A positive relationship was found between AChE activity and Tetraphyllidea fam. gen. sp., Anisakis physeteris and H. aduncum abundance and a negative one with the abundance of Cucullaninae gen. sp. LDH showed a positive relationship with the abundance of the parasites Paracyclocotyla cherbonnieri and Tetraphyllidea fam. gen. sp. At cyto-histological level, coccidians were detected in the pyloric caeca with a prevalence of 90% in Barcelona, but in the rest of organs almost no alterations were detected. The restricted macroplanktonic diet of A. rostratus, that maintains it distant from the sea-floor for longer periods than other demersal species, probably makes this species less susceptible to sediment-associated impacts including parasitism.

Food consumption of five deep-sea fishes in the Balearic Basin (western Mediterranean Sea): are there daily feeding rhythms in fishes living below 1000 m?

Predation and food consumption of five deep-sea fish species living below 1000 m depth in the western Mediterranean Sea were analysed to identify the feeding patterns and food requirements of a deep-sea fish assemblage. A feeding rhythm was observed for Risso's smooth-head Alepocephalus rostratus, Mediterranean grenadier Coryphaenoides mediterraeus and Mediterranean codling Lepidion lepidion. Differences in the patterns of the prey consumed suggest that feeding rhythms at such depths are linked with prey availability. The diets of those predators with feeding rhythms are based principally on active-swimmer prey, including pelagic prey known to perform vertical migrations. The diets of Günther's grenadier Coryphaenoides guentheri and smallmouth spiny eel Polyacanthonotus rissoanus, which did not show any rhythm in their feeding patterns, are based mainly on benthic prey. Food consumption estimates were low (<1% of body wet mass day(-1) ). Pelagic feeding species showing diel feeding rhythms consumed more food than benthic feeding species with no feeding rhythms.

Muscular cholinesterase and lactate dehydrogenase activities in deep-sea fish from the NW Mediterranean

Organisms inhabiting submarine canyons can be potentially exposed to higher inputs of anthropogenic chemicals than their counterparts from the adjacent areas. To find out to what extend this observation applies to a NW Mediterranean canyon (i.e. Blanes canyon) off the Catalan coast, four deep-sea fish species were collected from inside the canyon (BC) and the adjacent open slope (OS). The selected species were: Alepocephalus rostratus, Lepidion lepidion, Coelorinchus mediterraneus and Bathypterois mediterraneus. Prior to the choice of an adequate sentinel species, the natural variation of the selected parameters (biomarkers) in relation to factors such as size, sex, sampling depth and seasonality need to be characterised. In this study, the activities of cholinesterases (ChEs) and lactate dehydrogenase (LDH) enzymes were determined in the muscle of the four deep-sea fish. Of all ChEs, acetylcholinesterase (AChE) activity was dominant and selected for further monitoring. Overall, AChE activity exhibited a significant relationship with fish size whereas LDH activity was mostly dependent on the sex and gonadal development status, although in a species-dependent manner. The seasonal variability of LDH activity was more marked than for AChE activity, and inside-outside canyon (BC–OS) differences were not consistent in all contrasted fish species, and in fact they were more dependent on biological traits. Thus, they did not suggest a differential stress condition between sites inside and outside the canyon.

Are deep-sea organisms dwelling within a submarine canyon more at risk from anthropogenic contamination than those from the adjacent open slope? A case study of Blanes canyon (NW Mediterranean)

Due to their geomorphological structure and proximity to the coastline, submarine canyons may act as natural conduit routes for anthropogenic contaminants that are transported from surface waters to the deep-sea. Organisms dwelling in these canyon environments might thus be at risk of experiencing adverse health effects due to higher pollution exposure. To address this question, chemical and biochemical analyses were conducted on two of the most abundant deep-sea fish species in the study area, namely Alepocephalus rostratus and Lepidion lepidion, and the most abundant deep-sea commercial decapod crustacean Aristeus antennatus sampled inside Blanes canyon (BC) and on the adjacent open slope (OS). Persistent organic pollutants (POPs) levels, including polychlorinated biphenyl (PCB), dichlorodiphenyltrichloroethane (DDT) and derivatives, hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB) were determined in muscle tissue of selected samples from 900m and 1500m depth. Potential effects resulting from contaminant exposure were determined using hepatic biomarkers such as ethoxyresorufin-O-deethylase (EROD), pentoxyresorufin-O-deethylase (PROD), catalase (CAT), carboxylesterase (CbE), glutathione-S-transferase (GST), total glutathione peroxidase (GPX), glutathione reductase (GR) and superoxide-dismutase (SOD) enzyme activities and lipid peroxidation levels (LP). L. lepidion and A. antennatus tissues exhibited higher POP levels inside BC compared to the OS at 900m depth. These findings were consistent with biomarker data (i.e. enzymatic response to presence of contaminant agents). Elevated xenobiotic-metabolizing (EROD and PROD) and antioxidant enzymes (CAT and GPX) indicated higher contaminant exposure in both species caught within BC. No difference in POP accumulation between sites was observed in L. lepidion at 1500m depth, nor in biomarker data, suggesting that the pollution gradient was less pronounced at greater depths. This trend was further corroborated by the results obtained for A. rostratus at 1500m depth. Hence, the present findings suggest the, at least temporary, existence of a pollution gradient between Blanes canyon and the open slope at shallower depths and this resulted in alterations of the physiology of deep-sea organisms dwelling within this area.

Biliary PAH and Alkylphenol Metabolites, Biomarker Enzyme Activities, and Gene Expression Levels in the Deep-Sea Fish Alepocephalus rostratus

Biliary polycyclic aromatic hydrocarbon (PAH) and alkylphenol (AP) metabolites, hepatic gene expression, and corresponding enzyme activities were determined in the deep-sea fish Alepocephalus rostratus from two sites within the Mediterranean. Biliary metabolites included the hydroxylated PAH metabolites (OH-PAHs) 1-naphthol, 2-naphthol, 9-fluorenol, 9-phenanthrol, and 1-pyrenol and the APs 4-nonylphenol (NP) and 4-tert-octylphenol (OP). Five biomarker genes, namely, cytochrome P450 1A (CYP1A), vitellogenin (Vtg), catalase (CAT), Cu/Zn-superoxide-dismutase (Cu/Zn-SOD), and glutathione reductase (GR), were quantified using qRT-PCR. Moreover, corresponding enzyme activities (ethoxyresorufin-O-deethylase (EROD), CAT, SOD, and GR) were also determined. The ΣOH-PAHs detected ranged from 21.1 to 300.3 ng/g bile and were mainly composed of 1-naphthol. Both NP and OP metabolites were detected in all samples with concentrations ranging from 17.4 to 107.2 ng/g bile and 4.9 to 17.3 ng/g bile, respectively, and levels were significantly higher in samples from the western Mediterranean (WM) compared to those from the Catalan slope (CS). Accordingly, gene expression was significantly induced in male fish from the WM; however, these results were not reflected in enzyme activity levels. In particular, males caught at 2000 m in the WM exhibited 35-times higher Vtg levels compared to those from the CS, suggesting that endocrine-disrupting effects may potentially be occurring in such remote environments as the deep-sea.

Deep-sea macroplankton distribution (at 400 to 2300 m) in the northwestern Mediterranean in relation to environmental factors

Changes in the composition and biomass distribution of deep-living zooplankton over wide gradients of depth (400–2300m) and longitude (~180km) have been analyzed in the Balearic Basin (western Mediterranean), seeking the environmental variables responsible for these changes. Zooplankton tends to aggregate at different levels of the water column (forming Deep Scattering Layers, DSL) and in the Benthic Boundary Layer (BBL). Macrozooplankton biomass and composition were analyzed along a transect performed in July 2010 in midwater (between ~350 and 450m) and near the bottom (at ~5–200mab), over soundings of 450–2263m, including the top of Valencia Seamount (at ~40° 25′ N–02° 42′ E, 1076m). Zooplankton changed significantly in composition at the mesoscale (~180km) in both the DSL and the BBL. Siphonophores and calanoid copepods were the most dominant deep zooplankton taxa, calanoids reaching higher abundance in the BBL (1761–5177 individuals/1000m3) than in the DSL (1568–1743 individuals/1000m3). There was a significant increase in near-bottom zooplankton biomass over the middle slope, at 1000–1300m, linked to an increase in scyphozoans and siphonophores (Lensia spp. and Abylopsis tetragona) with peaks of 1.5–2.0gWW/1000m3. The peak of near-bottom zooplankton at 1000–1300m coincided with the lowest temperatures (13.08°C) and maximum O2 concentration (4.40ml/l) near the bottom and below 1000m with higher records in near-bottom turbidity. Gelatinous zooplankton are the main prey in the diet of the demersal fish Alepocephalus rostratus in the western Mediterranean, fish responsible for the peak of megafauna biomass reported at around 1200–1400m in the deep Mediterranean and at similar depths in other oceanic areas (e.g. the NW Atlantic). We suggest that deep-sea environmental conditions can govern peaks of near-bottom zooplankton, as well as influence the structure of the demersal fish community.

Legacy and emergent persistent organic pollutants (POPs) in NW Mediterranean deep-sea organisms

The levels and profiles of organochlorine (OC) contaminants, including polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethanes (DDTs), hexachlorocyclohexanes (HCHs) and penta- (PeCB) and hexachlorobenzene (HCB), as well as polybrominated diphenyl ethers (PBDEs) were determined in muscle samples of the deep-sea fish Alepocephalus rostratus, Coelorinchus mediterraneus and Lepidion lepidion and the red-shrimp Aristeus antennatus from the NW Mediterranean Sea. Mean PCB and DDT levels ranged from the highest concentrations in the fish A. rostratus (Σ7PCBs 6.93±0.71ng/gw.w. and ΣDDTs 8.43±1.10ng/gw.w.) to the lowest concentrations in the crustacean A. antennatus (Σ7PCBs 1.17±0.24ng/gw.w. and ΣDDTs 2.53±0.26ng/gw.w.). The concentrations of ΣHCHs and HCB were more than one order of magnitude lower, ranging from 0.07–0.36ng/gw.w. and 0.03–0.15ng/gw.w., respectively, while PeCB was only detected in a few samples. PBDE levels were approximately ten times lower than PCB and DDT concentrations, ranging from 0.47±0.20ng/gw.w. in A. antennatus to 0.92±0.13ng/gw.w. in A. rostratus. The high-molecular-weight PCBs 153, 138 and 180 represented 69–79% of Σ7PCBs in fish and 60% in the red shrimp. Moreover, in fish, the main DDT compound detected was the metabolite p,p′-DDE (70–80% of ΣDDTs), indicative of old DDT residues. In contrast, o,p′-DDE was the main DDT metabolite (49% of ΣDDTs) in shrimp, while the parent compound p,p′-DDT and its metabolite p,p′-DDE exhibited similar proportions of 16% and 21%, respectively. For PBDEs, the most abundant congeners were BDEs 28, 47, 99, 100 and 154 in fish (>70% Σ14PBDEs), while BDEs 153 and 209 were also important in A. antennatus, suggesting different uptake and/or biotransformation rates of PBDEs between fish and crustacea. In this sense, the ratios BDE 99/100, BDE 153/154, and BDE 47/99 were determined as proxies for BDE metabolization capacities and contrasted among species.

Natural variability of hepatic biomarkers in Mediterranean deep-sea organisms

Biomarker assays are widely used as proxies for contaminant-induced effects in aquatic organisms. However, in many cases, their intrinsic natural variability due to exogenous and endogenous factors makes the interpretation of biomarker data difficult. In the present study, we investigated the natural fluctuations of six hepatic biomarkers, namely ethoxyresorufin-O-deethylase (EROD) in fish and pentoxyresorufin-O-deethylase (PROD) in crustacea, catalase (CAT), carboxylesterase (CbE), glutathione-S-transferase (GST), total glutathione peroxidase (GPX) and glutathione reductase (GR) in two deep-sea fish species, namely Alepocephalus rostratus and Lepidion lepidion and the decapod crustacean Aristeus antennatus. The NW Mediterranean deep-sea environment is characterized by very stable temperature and salinity conditions, allowing the exclusion of these two factors as potential sources of interference with biomarker activities. Biomarker results exhibited a clear influence of reproductive processes on enzyme activities, in particular in A. rostratus, which presented a pronounced seasonal pattern linked to variations in the gonadosomatic index (GSI). In addition, other factors such as food availability may also have influenced the observed variability, in particular in specimens of L. lepidion, which did not exhibit variations in reproductive activity throughout the sampling period. Depth-related variability did not exhibit a clear trend and fluctuations across sampling depths were not attributable to any specific factor. Body size had also a significant influence on some biomarkers, although allometric scaling of certain enzyme activities appears to be species-specific. The present work has thus shown that despite the lack of fluctuations of abiotic parameters such as temperature and salinity, biomarker activities in deep-sea organisms still exhibit significant variability, mainly as a result of reproductive processes and food availability.

Differences in cytochrome P450 enzyme activities between fish and crustacea: Relationship with the bioaccumulation patterns of polychlorobiphenyls (PCBs)

Variations in cytochrome P450 enzyme (CYPs) distribution and function between animal groups could result in differential metabolism and elimination kinetics for certain contaminants. Although a number of studies have suggested that differences in polychlorobiphenyl (PCB) accumulation profiles between crustacea and fish might result from differential CYP patterns, the relationship between PCB bioaccumulation and CYP capacities has not been demonstrated in these organisms. In the present study we investigated the hepatic microsomal catalytic activities in three deep-sea fish species, Alepocephalus rostratus (Alepocephalidae), Coelorinchus mediterraneus (Macrouridae), and Lepidion lepidion (Moridae), and the decapod crustacean Aristeus antennatus (Decapoda), using six fluorescent CYP-mediated substrates, namely ER (7-ethoxyresorufin), PR (7-pentoxyresorufin), BR (7-benzyloxyresorufin), CEC (3-cyano-7-ethoxycoumarin), DBF (dibenzylfluorescein) and BFC (7-benzyloxy-4-trifluoromethylcoumarin). Furthermore, we related the metabolic activities to the accumulation patterns of 41 PCB congeners in the muscle of these organisms. The results indicated a marked difference in the presence and activities of CYP isoforms between fish and the crustacean A. antennatus. Liver microsomes of the three selected fish species were capable of metabolizing all six CYP-mediated substrates and enzymes were identified as primarily belonging to CYP1A and CYP3A subfamilies. In contrast, hepatopancreas microsomes from A. antennatus only showed activity for PR and DBF substrates, generally related to mammalian CYP2-like enzymes. Furthermore, a direct relationship between metabolic activities and PCB accumulation profiles could be established. Results revealed that A. antennatus accumulated significantly higher proportions of PCBs 28, 52, 118, 138, 158 and 169 than fish, which is in accordance with the previously observed lack of CYP1A-like biotransformation capacities. Moreover, A. antennatus exhibited lower levels of PCBs 87, 149, 153, 170, 180, 183, 194 and 206 indicating that this crustacean is able to metabolize congeners considered mammalian CYP2B inducers. Hence, the present findings highlight the role of CYP-mediated metabolism in the congener-specific accumulation of PCBs in aquatic organisms and stress the need to further investigate quantitative and qualitative differences in xenobiotic metabolism among animal groups.

Biodiversity of deep-sea demersal megafauna in western and central Mediterranean basins

Abundance, biomass and diversity patterns of bathyal and abyssal Mediterranean megafauna (fishes and invertebrates) were analyzed in the western Balearic Sea, the western Ionian Sea and the eastern Ionian Sea. Sampling was conducted with a Otter-trawl Maireta System (OTMS) at depths ranging from 600 to 4000 m. A series of ecological indicators were computed: total abundance and biomass, Margalef species richness, Shannon-Wiener diversity and Pielou’s index of evenness. A multidimensional scaling was applied, indicating that the megafauna communities were grouped by depth, while geographic area had a less defined influence. Margalef richness declined with depth in all three areas, but more steeply in the western Ionian Sea. Pielou’s evenness behaved differently in the three zones, showing a V-shaped curve in the eastern Ionian while showing a decreasing pattern in the other two areas. At lower slope depths, massive presence of the fishes Alepocephalus rostratus in the western basin and Bathypterois mediterraneus in the central basin caused a sharp reduction in evenness.

Deep-water fish assemblages in the central-western Mediterranean (south Sardinian deep-waters)

This paper explores structure and spatial distribution of fish assemblages in an area of the central-western Mediterranean Sea (south Sardinian deep-waters) at depths between 546 and 1598 m. A total of 67 species (12 chondrichthyes and 55 teleosteans) were sampled. Multivariate analysis showed a clear pattern of zonation. Three main assemblages were identified within the vertical range investigated: the first situated in the shallower area between 546 and 699 m, the second group between 720 and 1099 m, and the third between 1145 and 1598 m. Abundance values declined with increasing depth. Highest biomass values were found at depths of 720–1099 m with the presence of larger species such as Galeus melastomus, Mora moro, Trachyrhynchus scabrus and Alepocephalus rostratus. Species richness decreased with depth. The deepest bottoms of the central-western Mediterranean Sea shelter an ichthyofauna dominated by small to medium-sized species living in a food-scarce environment in which some large mobile fishes are widespread.

Influence of trawl type on the composition and diversity of deep benthopelagic fish and decapod assemblages off the Catalan coasts (western Mediterranean)

A series of 57 (600-750 m) and 32 (1184-1320 m) hauls were compiled to compare data from four trawl types in analyses of the species composition and diversity of deep benthopelagic fish and decapods off the Catalonian coasts (western Mediterranean). Two 1-warp trawls (OTSB-14 and OTMS-25) and two 2-warp trawls (a commercial trawl [CT] and a GOC73) were used, from hauls performed between 1988 and 2007 were compiled. At 600-750 m the OTSB-14 hauls were separated in multi-dimensional scaling (MDS) from hauls performed with MTS-25, CT, and GOC73. Ordination of hauls along DIM1 of MDS was significantly correlated (Spearman’s r) with mesh size at codend, bridle length, and vertical opening of trawls. When CT and GOC73 were compared with MTS-25, the most dissimilar species were Aristeus antennatus, Galeus melastomus and Trachyrhynchus scabrus . A particular case was A. antennatus , with a significantly higher abundance in MTS-25 catches than the rest of the trawls. At 1200 m the OTSB-14 and MTS-25 hauls were segregated in MDS analysis. DIM2 was correlated with the sampling period (month), indicating a temporal effect on haul composition. At 1200 m the main dissimilarities between OTSB-14 and MTS-25 were marked by Alepocephalus rostratus and A. antennatus (caught with MTS-25), and by Cataetyx alleni , the Notacanthidae Notacanthus bonapartei and Polyacanthonotus rissoanus , and Plesionika acanthonotus (caught with OTSB-14). As a conclusion, OTSB-14 showed a significantly higher abundance in catches than MTS-25, CT and GOC73, and a higher S (number of species) and J (equitability) than MTS-25. On the lower slope seasonality influenced trawl comparisons; however, it is likely that MTS-25, with higher vertical height than OTSB-14, caught the benthopelagic fish A. rostratus more efficiently, explaining the higher biomass from MTS-25 there. MTS-25 positively selected A. antennatus , in parallel to a negative catchability for other species.

Long-term changes in the composition and diversity of deep-slope megabenthos and trophic webs off Catalonia (western Mediterranean): Are trends related to climatic oscillations?

For depths ranging between 650 and 1700 m we have compared recent (2007–2008) to older (from 1988 to 1992) data, searching for long-term changes in the distribution, abundance and composition of deep megafauna (fish and decapods) off the central Catalonian coasts (western Mediterranean). Overall, in the depth interval between 600 and 1100 m, we found higher abundance of fish in 1988–1992 than in 2007, a decrease simultaneous with an increase of decapod crustaceans. Older and more recent haul replicates (after 20 years) had similar assemblage composition in the depth range 1300–1700 m, whereas we found significant changes at 1000 m. Diversity of fish was greater in 1988–1992 than in 2007, while diversity of decapod crustaceans increased between the two periods. Thus, there was a reorganization in benthopelagic communities, rather than a loss of biodiversity. This was in agreement with long-term changes described for diversity of (neritic) zooplankton in the western Mediterranean. We found a dominance of plankton-suprabenthos feeders (e.g. fish such as Lepidion lepidion, Hymenocephalus italicus and Alepocephalus rostratus; the decapods Plesionika spp. and Sergestes arcticus) in 1988–1992. In 2007 by contrast, dominance of plankton-suprabenthos feeders decreased, and assemblages were increasingly composed of benthos-feeding decapods (e.g. Aristeus antennatus, Pontophilus norvegicus and some hermit crabs) preying for instance on polychaetes. These results coincided with low/negative North Atlantic Oscillation index (NAO) in 2007 and in the period immediately before (2004–2006) 2007 (increase of benthos feeders), and with high average NAO in 1988–1992 (decrease of benthos feeders, which in turn may enhance abundance of plankton feeders). The benthic decapod Calocaris macandreae and suprabenthos (small crustaceans, mostly peracarids, living on and just beneath the sediment surface) are key prey in food webs off Catalonian margins, acting as links between surface oceanographic processes and abundance of benthopelagic predators. A conceptual model is presented relating changes in climatic conditions with changes in deep-sea, benthic-suprabenthic food webs. Calocari macandreae was more abundant in 2007, after 3 years of negative NAO. Under negative/low NAO, rainfall and river discharges increase in the NW Mediterranean, which may enhance advective food inputs for macrobenthos. This fits well with the higher abundance of benthos feeders in 2007, as well as with the significant deepening of decapod crustacean assemblages in that same period. Suprabenthos, being short-lived and annual species, were more abundant under positive NAO conditions (1988–1992), probably enhancing the abundance or aggregation of suprabenthic/pelagic feeders.

On the cephalic and pectoral girdle muscles of the deep sea fish Alepocephalus rostratus, with comments on the functional morphology and phylogenetic relationships of the Alepocephaloidei (Teleostei)

On the cephalic and pectoral girdle muscles of the deep sea fish Alepocephalus rostratus, with comments on the functional morphology and phylogenetic relationships of the Alepocephaloidei (Teleostei)

First observations on the reproduction of Alepocephalus rostratus Risso, 1820 (Osteichthyes, Alepocephalidae) from the Sardinian Channel (Central-Western Mediterranean)

Data are provided on the reproductive biology of a bathypelagic species Alepocephalus rostratus Risso, 1820 caught in the Sardinian Channel between 800 and 1200 m depth. The macroscopic and microscopic description of the gonads was based on 223 females and 95 males. Unlike most other teleosts, the testis is generally formed of two distinct subcylindrical lobes along the mid-line of the body cavity. A five-stage scale of development for both females and males was established based on the macroscopic and microscopic observation of the gonads. Biometric and histological analyses revealed synchronous development in the bilobed testis and ‘group-synchrony’ in the ovary. The temporal evolution of the gonadosomatic index and the monthly variations in the percentage distribution in the stages of ovarian development revealed an extended spawning period in this species.

New records of deep-water teleost fish in the Balearic Sea and Ionian Sea (Mediterranean Sea)

During an EC-funded research carried out in the Mediterranean Sea deep-water fish (600-4000 m) were collected in the Balearic Sea as well as the western and eastern Ionian Sea. Caelorhynchusmediterraneus is a new record for the Balearic Sea, Cyclothone braueri, Hygophum benoiti, Paralepis speciosa, Chalinura mediterranea, Coryphaenoides guentheri, C. mediterraneus, Lepidion lepidion and Cataetyx laticeps for the western Ionian Sea, and Polyacanthonotus rissoanus, C. guentheri, C. mediterraneus, L. lepidion and C. laticeps for the eastern Ionian Sea. The bathymetric distribution of other species has been updated. Species richness decreased with depth in the three surveyed areas, showing a significant shift below 1500 m. At depths greater than 1000 m macrourid and morid species were dominant except in the Balearic Sea, where Alepocephalus rostratus was found to be very abundant as deep as 1500 m. At depths greater than 1500 m the dominant species were Bathypterois mediterraneus, C. mediterranea and C. guentheri . The results of this research confirm the scarcity of deep fish fauna in the Mediterranean compared to the Atlantic. For the greatest depths are concerned, the faunistic difference between the western and eastern Mediterranean seems to be most probably due to a lesser number of investigations on the eastern side rather than any real paucity of ichthyofauna.

Trophic relationships in a Mediterranean deep-sea fish community: partition of food resources, dietary overlap and connections within the benthic boundary layer

Food resource partitioning and some trends in the feeding ecology of 13 species of fishes inhabiting the slope of the Catalan Sea (western Mediterranean) were examined. Specimens were collected from 1987 to 1991, using bottom trawls at depths between 1000 and 2250 m. Prey selection was also examined in relation to data collected in the same area on 2 potential prey compartments for fish, the benthopelagic macrofauna —suprabenthos or hyperbenthos— and the megafaunal decapod crustaceans. Thus, the possible connections with prey availability within the benthic boundary layer (BBL) were also analysed. The size of available food resources was the most important factor respon- sible for food resource partitioning, both by depth stratum and season. The importance of the variable predator size is also evidenced. Most of the deep-sea demersal fish species inhabiting the Catalano- Balearic slope often consumed a variety of available resources in their diets, mainly comprising suprabenthos, but also infauna or planktonic prey. Thus, the BBL macrofauna constitute an important part of the available food exploited, with the range of the prey consumed increasing for the largest predators. A significant trend to increase dietary H' values within the depth interval where each spe- cies attained its maximum abundance was observed. Some (positive) prey selection upon certain prey groups was detected depending on the fish species: sharks, Alepocephalus rostratus and Nettastoma melanurum preferentially preyed on decapods, siphonophores and pyrosomids; Polyacanthonotus rissoanus, macrourids, Lepidion lepidion and Cataetyx alleni preyed upon suprabenthic peracarid crustaceans; and only Bathypterois mediterraneus preferentially consumed copepods, the numeri- cally dominant group in the bathyal BBL. Resource partitioning was high among the fish assemblage analysed in relation to the generally low dietary overlap values recorded. Overall, dietary overlap values among fish species decreased with increasing depth.