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

15 pages, 3 figures, 5 tablesFood 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 responsible 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 H¹ values within the depth interval where each species 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 numerically 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 depthPeer Reviewe

Influence of trophic variables on the depth-range distributions and zonation rates of deep-sea megafauna: the case of the Western Mediterranean assemblages

17 pages, 6 figures, 5 tablesWe studied in a deep-sea megafaunal community the relationship of different trophic variables to the depth ranges inhabited by and depth zonation of species, after the ordination of fish and decapod crustaceans in feeding guilds. The variables studied included trophic level of species, food sources exploited, mean weight of predators and prey, feeding intensity and dietary diversity of species. We compiled data on the diets of 18 species of fish and 14 species of decapod crustaceans distributed between 862 and 2261 m in the Catalano-Balearic Basin (Western Mediterranean). Feeding guilds were identified for fish and decapods separately and at two depth strata (862–1400 and 1400–2261 m). The zonation rates (degree of depth overlap) between species within each trophic guild differed by guild and taxon (fish and decapods). The three guilds (G1, G2 and G3) of decapod crustaceans showed quite significantly distinct overlap. G1 (plankton feeders) showed the widest overlap (1326–1381 m) and G3 (benthos feeders) the narrowest (330–476 m). Among the four guilds established for fish, G1, comprising larger predators such as sharks, showed the lowest overlap (between 194 and 382 m). Macrourids overlap ranged between 122 and 553 m, the rest of benthopelagic feeders ranged between 423 and 970 m, and G3 (benthos feeders) gave overlaps between 867 and 1067 m. Significant differences were detected between the depth overlap of most feeding guilds excluding the paired comparisons between G1/macrourids, and G2/G3. Among decapods higher zonation rates (=lower depth overlap) were identified in those guilds occupying higher trophic levels (TL), with a similar, though not as general, trend among fish. In the ordination of species in feeding guilds, TL as indicated by δ15N measurements, was significantly correlated with Dimension 1 (D1) of ordination—MDS-analysis, both in fish and decapods at 862–1400 m. However, deeper (at 1400–2261 m), D1 was not significantly correlated with TL but with the mean weight of predator and prey in fish. In general, TL was again the main explanatory variable (accumulated variances, r2, explained by multi-linear regression—MLR-models between 0.54 and 0.69) both of the zonation rates and the depth ranges occupied by megafauna (fish and decapods together) throughout all the depth range studied. Possible relationships between zonation rates/depth distributions and other biological variables (i.e. egg size, fecundity) are also discussedThe authors are grateful for the assistance provided by all the participants of the research project BATIMAR (funded by C.I.C.Y.T.-M.E.C. of Spain)Peer reviewe

Life strategies and habitat preferences of two especialized fish species in the NW Mediterranean deep sea

VII International Symposium on Marine Sciences (ISMS 2020), 1-3 July 2020 (Barcelona).-- 2 pagesCataetyx alleni and Melanostigma atlanticum are two poorly known small-sized fishes showing peculiar features regarding their reproductive biology and behaviour (Silverberg et al., 1987; Follesa et al., 2011). Present research reveals different aspects regarding the biology and ecology of these species in the slopes of the Balearic basin. Specimens were collected during the last 30 years during different oceanographic cruises. Geographical/habitat distribution, population structure, diet, parasite infections and trends on biological indices were addressed. Higher population density of C. alleni was found in the mainland than in the insular slope of the Balearic basin and in the middle (ca. 800-1400 m depth) than in upper and lower slopes (ca. 200-800 and below 1400 m depth, respectively). M. atlanticum was only sampled in the mainland slope, mostly from upper and middle slopes and preferably south to submarine canyons, probably linked to sediment depocenters. For C. alleni, a bigger-deeper trend occurred for both sexes from spring to autumn. For M. atlanticum, this same pattern was observed for females and no seasonal trends were appreciated. Regarding diet, C. alleni intestinal fullness was highest in the upper slope in spring and in the middle slope in summer, and main diet items recovered comprised polynoid polychaetes, calanoid copepods, amphipods, isopods, mysids and decapods. M. atlanticum stomach fullness trends could only be observed in the upper slope, where it was higher in summer than in autumn, and main diet items recovered were calanoid copepods and polychaetes. Parasite assemblages of both species displayed low richness, diversity and abundance, and were largely composed by larval parasites, indicating a low-intermediate position within local food webs. Fo rC. alleni, gonadosomatic index peakedin autumn, coinciding with the reproductive season of this species, and condition factor increased in spring-summer and decreased with depth. Hepatosomatic index increasedin summer for both speciesThis study was supported by the CSIC and CAICYT project BATIMAR and by the MICYT projects BIOMARE, ANTROMARE and RECOMARESPeer reviewe

Diets and bathymetric distributions of two bathyal sharks of the Catalan deep sea (western Mediterranean)

10 pages, 4 figures, 3 tablesBathymetric distribution of Centroscymnus coelolepis has been studied. This species was restricted to the lower slope (1419 to 2251 m), where it was the only abundant shark. Galeus melastomus was abundant below 1000 m but became rare between 1400 and 1600 m, so that there is almost no bathymetric overlap with C. coelolepis. Greatest abundance of G. melastomus in the Catalan Sea was found in the upper slope. Diets of both species showed a very low overlap which is mainly attributed to the dietary specialization of C. coelolepis. Its diet is almost exclusively based on cephalopods. The diet of G. melastomus has been analyzed at depths below 1000 m. Its diet is more diverse than that of C coelolepis and cephalopods are not preferential prey. The upper and middle slope specimens of G. melastomus have a different diet; this difference may be the consequence of a change in available resources. Finally the trophic position of Etmopterus spinax, the third most abundant shark below 1000 m, seems to be more similar to that of C. coelolepis. These results suggest that a possible competition is more likely between C. coelolepis and E. spinax than between C. coelolepis and G. melastomus. This could explain the bathymetric displacement of C coelolepis in the western Mediterranean as a result of an interaction between species of higher trophic levelsPeer Reviewe

Life strategies and habitat preferences of Bythitidae and Zoarcidae, specialized fishes with particular life histories, in the Mediterranean deep sea

16 pages, 9 figures, 4 tables, supplementary data https://doi.org/10.1016/j.dsr.2021.103593Deep-sea habitats are home for a variety of yet poorly known fish species, some of which display specialized life strategies, as is the case of Bythitidae and Zoarcidae. With the purpose of elucidating biological and ecological aspects of representatives of these families in NW Mediterranean waters, a large dataset based on 599 specimens of Cataetyx alleni, 30 C. laticeps and 284 Melanostigma atlanticum captured during the last 30 years within the framework of different research projects was used to address their geographical and bathymetric distribution, population structure, reproduction, trophic ecology, parasitism and enzymatic markers in the Balearic basin. Present outcomes revealed a patchy distribution mostly for M. atlanticum, possibly related to aggregation during reproduction and to the association with specific sediments. For the three species, higher densities occurred in the mainland vs. the insular margin, and a diminishing trend in estimated densities over the last decades was observed for C. alleni and M. atlanticum likely linked to climatic oscillations. Trophic data indicated that the two Cataetyx species inhabit the water-sediment interface and mainly feed on suprabenthic prey, while M. atlanticum inhabits the water column near the bottom preying on pelagic organisms and moving towards the seabed during reproduction. These results were supported by the parasitological assessment, which revealed that parasite communities were moderately diverse and abundant for Cataetyx spp. while being highly depauperate for M. atlanticum. Present outcomes from the Mediterranean Sea confirmed reproduction of C. alleni during autumn-winter and of M. atlanticum during autumn. Spawning of the former species may occur in winter-spring, as suggested by the finding, by the first time, of two females captured in March with fully-developed embryos inside. Levels of enzymatic markers quantified in muscle were provided for C. alleni and M. atlanticum for the first time. The special interactions found between the distribution and biology of Bythitidae and Zoarcidae and the sedimentary bottoms that they inhabit indicates that such conventional habitats are more heterogeneous than it is generally assumed and deserve higher attention for future protectionThis work was supported by the Spanish National Research Council (CSIC) and the Spanish Scientific and Technic Research Assessing Commission (CAICYT) projects BATIMAR (grant number PAC 86–008/ID 821) and RETRO (grant number MAR90/757), and by the Spanish Ministry of Science and Innovation (MICYT) projects BIOMARE (grant number CTM2006-13508-C02-01/MAR), ANTROMARE (grant numbers CTM2009–12214–C02–01/MAR and CTM2009–12214–C02–02/MAR) and RECOMARES (gran number RTI2018-094066-B-100)Peer reviewe

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

21 pages, 7 figures, 3 tablesPredation and food consumption of five deep-sea fish species living below 1000m 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. © 2014 The Fisheries Society of the British IslesThe work developed within the project ANTROMARE (ref. CTM2009-12214-C02-01-MAR and CTM2009-12214-C02-02-MAR) financed by the Spanish Ministry of Science and Innovation made possible the realization of the analyses included in this article. Data came out from the project BATIMARPeer Reviewe

Hepatic biomarkers of xenobiotic metabolism in eighteen marine fish from NW Mediterranean shelf and slope waters in relation to some of their biological and ecological variables

8 pages, 2 figures, 3 tablesA suite of hepatic biomarkers currently used in pollution monitoring were measured in eighteen common fish species, comprising five orders, eleven families of teleosts and two elasmobranchs. The sampling was carried out seasonally in front of the Barcelona coast (NW Mediterranean) during 2007. The hepatic enzymes considered were the activities of catalase, glutathione reductase, ethoxyresorufin O-deethylase, carboxylesterase and glutathione S-transferase. As markers at higher levels of biological organization, feeding preferences (on benthic, suprabenthic or zooplanktonic species), swimming capability, stomach fullness and trophic level were considered. Significant species differences were found among all the biochemical parameters analysed, although no relationships among the biomarkers themselves were evidenced. In general enzymatic activities were much higher in teleosts than in elasmobranchs, and in perciforms than in gadiforms. Seasonality was observed in some species with higher activities usually corresponding to the winter period. No site related differences were observed in the two selected sites, which differ over a small pollution gradient. A multivariate canonical Correspondence analysis (CCA) was performed on shelf and slope species separately to relate biochemical markers with ecological variables. CCA revealed that for shelf species, EROD was positively related to benthos feeding as well as trophic level, while on the slope the clearest association was between suprabenthos feeders and trophic level. Our present results, including seasonality, slightly differ from former observations (Solé et al., 2009a) and reveal a more significant role of the ecological variables in controlling biomarkers expression in fish from the shelfThis work was financed by the Spanish Science and Technology Ministry project BIOMARE (CTM2006-13508-CO2-02/MAR) and Complementary Action (CTM2006-28145-E/MAR). ACA (Agencia Catalana de l’Aigua, Generalitat de Catalunya) is acknowledged for providing data on organic pollutants in sedimentPeer reviewe

To what extent can specialized species succeed in the deep sea? The biology and trophic ecology of deep-sea spiny eels (Notacanthidae) in the Mediterranean Sea

17 pages, 9 figures, 7 tablesThe population structure, reproductive biology and feeding ecology of the two notacanthids inhabiting the deep Mediterranean, Notacanthus bonapartei and Polyacanthonotus rissoanus, were analyzed in the Balearic Basin at depths from 579 to 2233 m (mainly pristine depths or subjected to low fishing impact), including seasonal variations. Preferred average depths (Centres of Gravity, CoG) of Notacanthusbonapartei were situated over the middle slope (942 m) and of P. rissoanus on the lower slope (1680 m). For both species, bigger individuals collected at the deepest depths had the highest values of a gonadosomatic index (GSI), suggesting that in reproductive periods adults migrate into deeper waters. The reproductive season for N. bonapartei was late summer and autumn; that of P. rissoanus was narrower, restricted to summer. N. bonapartei exploited benthic prey, among identified prey mainly echinoderms (e.g., Penilpidia ludwigi, Hymenodiscus coronata) and sessile benthic organisms (e.g., actinians and polyps of the bamboo coral Isidella elongata). Consumption of bamboo coral polyps by N. bonapartei constitutes a unique specialized trophic strategy and a direct link with such corals. Some differences in the diet composition related to depth were observed, as were a few differences related to periods of water-column stratification and homogenization. Gut fullness (F) of this species was mainly correlated with surface Chlorophyll a recorded 2–3 months before sampling date and somewhat but less so with river discharges 1 month before sampling. That suggests that vertical flux of organic matter was the food source for prey exploited by N. bonapartei. Diet of P. rissoanus was based on epibenthic-suprabenthic crustaceans, e.g. tanaids (Apseudes spp.), isopods (Munnopsurus atlanticus) and amphipods (Rhachotropis caeca) and on polychaetes (Polynoidae, Harmothoe spp.), all these prey more mobile than consumed by N. bonapartei. No significant differences in diet composition were found related with either depth or homogenization/stratification of the water column. This lack of changes in diet is probably attributable to the greater stability of the lower slope where P. rissoanus lives. Gut fullness was mainly correlated with surface Chlorophyll a recorded simultaneously with the fish sampling. Lactate dehydrogenase (LDH) activity was similar in the muscle of the two notacanthids (N. bonapartei=3.72–8.75 µmol/min/mg prot; P. rissoanus=7.56 µmol/min/mg prot). Values for N. bonapartei were the highest found compared to other deep-sea fish in the deep Mediterranean. This could be related with the special feeding behaviour of this species when it removes sessile prey from substrateThis study was performed within the MICYT project ANTROMARE, and continued thanks to the multi-methological approach done in proposals like TREND (CTM2014-54018-C3), though not financed by MINECO evaluatorsPeer Reviewe

A parasitological survey of Galeus melastomus Rafinesque, 1810 from deep waters of the NW Mediterranean sea in relation to diet and health condition of the host

9th International Symposium on Fish Parasites (ISFP), 31st of August to 4th of September 2015, Valencia, SpainDespite their importance and vulnerability, deep-dwelling elasmobranchs are still poorly understood. In this context, this study aims to perform a parasitological survey of the blackmouth catshark Galeus melastomus Rafinesque, 1810 in deep waters of the north-western Mediterranean Sea describing variability on the parasite community between host maturity stages and its relation to diet and health condition of the host. A total of 120 specimens of G. melastomus were captured in 2010-2011 at 400-1,400 m depth in three different locations of the Balearic basin using a semi-balloon ottertrawl. Parasitological, dietary, enzymatic stress indicators and histological data were obtained according to standardized protocols. Main relationships among fish parasite load, size, condition indices, enzymatic activity of muscular acetylcholinesterase, lactate dehydrogenase and citrate synthase and intensity of hepatic melano-macrophages were tested. A total of 16 different parasite taxa were found: one coccidian, one monogenean, one digenean, five cestodes, seven nematodes and one copepod. The most important parasites in terms of prevalence and abundance showed a significant relationship with host size, probably reflecting hosts ontogenic diet shifts: the digenean Otodistomum sp., the cestodes Scolex pleuronectis and Grillotia cf. adenoplusia and the copepod Eudactylina cf. vilelai were linked to adult sharks, while the cestode Ditrachybothridium macrocephalum characterized juvenile hosts. Overall results considering associations between parasite infection parameters and health condition of their hosts yield the conclusion that, in the present study, the intensity of parasite infections does not negatively affect fish health.The study was supported by the MICINN project ANTROMARE (CTM2009-12214-C02-02)Peer Reviewe