Feeding ecology and trophic position of three sympatric demersal chondrichthyans in the northwestern Mediterranean

14 pages, 5 figures, 3 tables, supplementary material http://dx.doi.org/10.3354/meps11188Understanding how marine predators interact is a scientific challenge. In marine ecosystems, segregation in feeding habits has been largely described as a common mechanism to allow the coexistence of several competing marine predators. However, little is known about the feeding ecology of most species of chondrichthyans, which play a pivotal role in the structure of marine food webs worldwide. In this study, we examined the trophic ecology of 3 relatively abundant chondrichthyans coexisting in the Mediterranean Sea: the blackmouth catshark Galeus melastomus, the velvet belly lanternshark Etmopterus spinax and the rabbit fish Chimaera monstrosa. To examine their trophic ecology and interspecific differences in food habits, we combined the analysis of stomach content and stable isotopes. Our results highlighted a trophic segregation between C. monstrosa and the other 2 species. G. melastomus showed a diet composed mainly of cephalopods, while E. spinax preyed mainly on shrimps and C. monstrosa on crabs. Interspecific differences in the trophic niche were likely due to different feeding capabilities and body size. Each species showed different isotopic niche space and trophic level. Specifically, C. monstrosa showed a higher trophic level than E. spinax and G. melastomus. The high trophic levels of the 3 species highlighted their important role as predators in the marine food web. Our results illustrate the utility of using complementary approaches that provide information about the feeding behaviour at short (stomach content) and long-term scales (stable isotopes), which could allow more efficient monitoring of marine food-web changes in the study areaM.A.-P. was supported by a predoctoral fellowship of the FPI program (Spanish Ministry of Economy and Competitiveness). J.N. was supported by a research contract of the Marie Curie GIC project BioWeb. M.C. and J.A. are supported by a post-doctoral contract of the Ramon y Cajal Program (Spanish Ministry of Economy and Competiveness), and M.C. was also supported by BioWeb project. This study is a contribution to the project ECOTRANS (CTM2011-26333, Ministerio de Economía y Competitividad, Spain)Peer Reviewe

Estudio de referencia sobre la distribución de basura marina en fondos blandos asociados a caladeros de pesca de arrastre en el mediterráneo norte

9 pages, 5 figures, 6 tables[EN] The present study aims to analyse the local and regional variability in the density and typology of marine debris on fishing grounds on the northern Mediterranean continental shelf, and to test relationships between marine litter and trawl fishing activity. Moreover, the colonization of plastics was examined in order to study the importance of plastics as a source of impact on marine communities and their further environmental implications. This study surveyed 11 sites, associated with trawling grounds and subjected to different levels of fishing intensity, located in four areas of the Mediterranean: one in Italy, the Central Tyrrhenian coast, one in Greece, the eastern Ionian coast, and two in Spain, the Murcian and Catalan coasts. Samples were collected during an oceanographic cruise undertaken from the 21 May to the 24 June 2009. Results showed geographical variation in the density of marine debris which ranged from 0 to 405 pieces per hectare in the surveyed areas, plastics being the dominant components. Variability within sites was higher than between areas, indicating small-scale patchiness in the distribution of the debris over the seafloor. Though the study areas were within trawling grounds, the density of debris was not significantly correlated with fishing effort. More than 30% of plastics were between 10 and 20 cm width/length, and more than 40% of the plastics were colonized by a biofilm of microorganisms, suggesting indirect effects on benthic communities[ES] Este estudio tiene como objetivo analizar la variabilidad local y regional de la basura marina en caladeros de pescas de la plataforma continental mediterránea septentrional y estudiar la relación entre ésta y la actividad pesquera. En este estudio se examinaron once estaciones de muestreo asociadas a caladeros de pesca, sujetas a distintos niveles de esfuerzo y situadas en 4 áreas en el Mediterráneo: una en Italia, en la costa central del Tirreno (TC), otra en Grecia, en la costa jónica occidental (IC) y otras dos en España, en las costas murciana y catalana (MC y CC). Las muestras se obtuvieron durante una campaña oceanográfica llevada a cabo entre el 21 de mayo y el 24 de junio de 2009. Los resultados mostraron una variación geográfica en la densidad de basura marina comprendida entre 0 y 405 piezas por hectárea en las áreas muestreadas, siendo los plásticos el componente principal. La variabilidad entre estaciones resultó más alta que la variabilidad entre áreas, lo que indica una heterogeneidad a pequeña escala en la distribución de la basura sobre el fondo. Aunque las áreas de estudio estaban situadas en caladeros pesqueros, la densidad de basura no mostró una correlación significativa con el esfuerzo de pesca. Más del 40% de los plásticos se encontraron colonizados por un biofilm de microorganismos y más del 40% presentaba dimensiones de entre 10 y 20 cm ancho/largo. Se examinó la colonización de los plásticos con el fin de estudiar su importancia como fuente de impacto en las comunidades marinas y sus posibles implicaciones ambientalesData used in this work were collected in the framework of the research project COMSOM (CTM2008-04617/MAR) funded by the Spanish “Ministerio de Ciencia e Innovación”. We thank our colleagues A. Ligas, M. Sartini, Ch. Mytilineou, K. Papadopoulou, P. Sartor and P. Martín for their collaboration. The authors wish to thank to the crew of the V/R Garcia del Cid and the participants of the oceanographic cruisePeer reviewe

Assessing Fishing and Marine Biodiversity Changes Using Fishers’ Perceptions: The Spanish Mediterranean and Gulf of Cadiz Case Study

15 pages, 11 figures, 4 tables, 2 annex, 3 tables supporting information http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0085670Background: The expansion of fishing activities has intensively transformed marine ecosystems worldwide. However, available time series do not frequently cover historical periods. Methodology: Fishers’ perceptions were used to complement data and characterise changes in fishing activity and exploited ecosystems in the Spanish Mediterranean Sea and Gulf of Cadiz. Fishers’ interviews were conducted in 27 fishing harbours of the area, and included 64 fishers from ages between 20 to > 70 years old to capture the experiences and memories of various generations. Results are discussed in comparison with available independent information using stock assessments and international convention lists. Principal Findings: According to fishers, fishing activity substantially evolved in the area with time, expanding towards deeper grounds and towards areas more distant from the coast. The maximum amount of catch ever caught and the weight of the largest species ever captured inversely declined with time. Fishers (70%) cited specific fishing grounds where depletion occurred. They documented ecological changes of marine biodiversity during the last half of the century: 94% reported the decline of commercially important fish and invertebrates and 61% listed species that could have been extirpated, with frequent mentions to cartilaginous fish. Declines and extirpations were in line with available quantitative evaluations from stock assessments and international conventions, and were likely linked to fishing impacts. Conversely, half of interviewed fishers claimed that several species had proliferated, such as cephalopods, jellyfish, and small-sized fish. These changes were likely related to trophic cascades due to fishing and due to climate change effects. The species composition of depletions, local extinctions and proliferations showed differences by region suggesting that regional dynamics are important when analysing biodiversity changes. Conclusions/Significance: Using fishers’ perceptions, fishing and ecological changes in the study area were documented. The recovery of local ecological knowledge provides valuable information complementing quantitative monitoring and evaluation surveysMC was supported by the Marie Curie EC CIG grant to BIOWEB and the Spanish Research Program Ramon y Cajal. GG was funded through the EC program Science in Society EC. FP7 (ref # 266544-GAP2)Peer reviewe

Short‑ and long‑term importance of small sharks in the diet of the rare deep‑sea shark Dalatias licha

11 pages, 3 figures, 4 tablesKnowing the trophic ecology of marine predators is essential to develop an understanding of their ecological role in ecosystems. Research conducted on deep-sea and threatened shark species is limited. Here, by combining analyses of individual stomach contents and stable isotope values, we examined the trophic ecology (dietary composition and trophic position) of the kitefin shark Dalatias licha, a deep-sea shark considered as near threatened globally and as data deficient in the Mediterranean Sea. Results revealed the importance of small sharks in the diet of the kitefin shark at short- and long-term scales, although finfish, crustaceans and cephalopods were also found. Predation on sharks reveals the high trophic position of the kitefin shark within the food web of the western Mediterranean Sea. Stable isotope values from liver and muscle tissues confirmed our results from stomach content analysis and the high trophic positionJN and MC were supported by a research contract of the Marie Curie Career Integration Grant Fellowships to the BIOWEB project. MC was also funded by a postdoctoral contract of the Ramon y Cajal Program (Spanish Ministry of Economy and Competiveness). CB was supported by a doctoral fellowship CONICYT-Becas Chile. This study forms a contribution to the project ECOTRANS (CTM2011-26333, Ministerio de Economía y Competitividad, Spain)Peer reviewe

Feeding ecology and ecological role of three large pelagic fish Sarda sarda, Xiphias gladius, and Euthynnus alletteratus in the Western Mediterranean Sea

The 3rd CLIOTOP Symposium,14-18 September 2015, San Sebastian, SpainPeer Reviewe

Year-round energy dynamics of sardine and anchovy in the north-western Mediterranean Sea

11 pages, 8 figures, 2 tablesVariability in body condition and energy storage has important implications for fish recruitment and ecosystem structure. Understanding strategies for energy allocation to maintenance, reproduction and growth is essential to evaluate the state of the fish stocks. In this study, we address the energetics dynamics of the annual cycle of anchovies (Engraulis encrasicolus) and sardines (Sardina pilchardus) in the north-western Mediterranean Sea using indirect and direct condition indices. We assessed and validated the use of morphometric, biochemical and energetic indices for both species. Annual patterns of the relative condition index (Kn), gonadosomatic index (GSI), lipid content (% lipids) and energy density (ED) were linked to the energy allocation strategy. Our results highlight that anchovy mainly rely on income energy to reproduce, while sardine accumulate the energy during the resting period to be used in the reproduction period. Consequently, variability in the lipid content and ED between seasons was lower in anchovy than in sardine. In both species, we observed an early decline in energy reserves in late summer-early fall, which may be related to unfavourable environmental conditions during spring and summer. Regarding the use of different condition indices, both direct indices, lipid content and ED, were highly correlated with Kn for sardine. ED was better correlated with Kn than lipid content for anchovy. For the first time, a relationship between ED of gonads and GSI for sardine and anchovy was provided, highlighting the importance of the energy invested in reproduction. This work provides new insights into the energy dynamics of sardine and anchovy. We also demonstrate which are the most suitable indices to measure changes in the physiological condition of both species, providing tools for the future monitoring of the populations of these two commercially and ecologically important fish speciesThis study was funded by ECOTRANS (Ministry of Economy and Competitiveness, Spain; CTM2011-26333) and PELWEB (Ministry of Science and Innovation, Spain; ES-PN-2017-CTM2017-88939-R) projects. A.A.-P was funded by a Predoctoral reserach grant (Ministry of Economy and Competitiveness, Spain; CTM2011-26333). J.N. was funded by a Ramon y Cajal contract (Ministry of Science and Innovation, Spain ;RYC-2015-17809With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)Peer reviewe

Morphological parameters of abundant and threatened chondrichthyans of the northwestern Mediterranean Sea

6 pages, 2 figures, 2 tablesThe diversity of chondrichthyans in the Mediterranean Sea is relatively high; however, available data indicate that this group is declining in abundance and several species are becoming rare. As a result, the collection of biological data is a priority for demographic models, stock assessments, and food web analysis. In the present study, we report morphological parameters and length–weight relationships of several chondrichthyan species, both abundant and threatened, from the western Mediterranean Sea. Samples were obtained with commercial and scientific bottom trawl vessels between 2001 and 2013. A total of 893 individuals belonging to 11 families and 20 species were weighed and total lengths measured. In addition, seven species of large demersal sharks were measured and length–length relationships obtained to study the relationships between different body length measurements. All species showed positive allometric or isometric growth, except for Centroscymnus coelolepis. The results of the length–weight relationships reveal differences between the western Mediterranean and nearby areas, depending on the species studiedCB was supported by a predoctoral fellowship CONICYT- Becas Chile. JN and MC were supported by a research contract of the Marie Curie Career Integration Grant Fellowships to the BIOWEB project. MC was also funded by a postdoctoral contract of the Ramon y Cajal Program (Spanish Ministry of Economy and Competiveness). This study forms a contribution to the project ECOTRANS (CTM2011-26333, Spanish Ministry of Economy and Competiveness, Spain)Peer Reviewe

Morphological parameters of abundant and threatened chondrichthyans of the northwestern Mediterranean Sea

6 pages, 2 figures, 2 tablesThe diversity of chondrichthyans in the Mediterranean Sea is relatively high; however, available data indicate that this group is declining in abundance and several species are becoming rare. As a result, the collection of biological data is a priority for demographic models, stock assessments, and food web analysis. In the present study, we report morphological parameters and length–weight relationships of several chondrichthyan species, both abundant and threatened, from the western Mediterranean Sea. Samples were obtained with commercial and scientific bottom trawl vessels between 2001 and 2013. A total of 893 individuals belonging to 11 families and 20 species were weighed and total lengths measured. In addition, seven species of large demersal sharks were measured and length–length relationships obtained to study the relationships between different body length measurements. All species showed positive allometric or isometric growth, except for Centroscymnus coelolepis. The results of the length–weight relationships reveal differences between the western Mediterranean and nearby areas, depending on the species studiedCB was supported by a predoctoral fellowship CONICYT- Becas Chile. JN and MC were supported by a research contract of the Marie Curie Career Integration Grant Fellowships to the BIOWEB project. MC was also funded by a postdoctoral contract of the Ramon y Cajal Program (Spanish Ministry of Economy and Competiveness). This study forms a contribution to the project ECOTRANS (CTM2011-26333, Spanish Ministry of Economy and Competiveness, Spain)Peer Reviewe

Eating the neighbours: importance of small sharks in the diet of the rare deep-sea shark Dalatias licha

V Jornadas Ibéricas de Ictiología SIBIC, Conhecer para preservar, 24-27 June 2014, Lisboa .-- 1 pageKnowing the feeding habits of marine predators is essential to understanding their ecological role in the ecosystem. Such knowledge can also inform conservation strategies for threatened species. Research conducted on shark species inhabiting the deep sea is very scarce although these species may play a relevant role in the dynamics of the ecosystem. In the present study, we aimed to examine the feeding ecology (dietary composition and trophic level) of the kitefin shark (Dalatias licha), a deep-sea shark globally considered as Near Threatened and as Data Deficient in the Mediterranean Sea. In particular, by combining the use of stomach content and stable isotopic approaches, we aimed to examine the main feeding strategies of this marine predator at different temporal scales in the western Mediterranean Sea. The results revealed the clear importance of small sharks in the diet of the kitefin shark at different temporal scales, although fin-fish, crustaceans and cephalopods were also found to make up part of its diet. This feeding behaviour also indicates its position as an important predator within the food web of the western Mediterranean deep Sea. Our results provide direction for further studies on the role that predatory species play in Mediterranean food websPeer Reviewe

Feeding ecology and ecological role of the Atlantic bonito Sarda sarda in the Northwestern Mediterranean Sea

IV Congress of Marine Sciences, 11-13 June 2014, Las Palmas de Gran Canaria.-- 1 pageKnowing the feeding habits of marine predators is essential to understand their ecological role in the ecosystem. Moreover, this information is pivotal for an accurate management and conservation strategies of their populations. The Atlantic bonito Sarda sarda is an epipelagic Scombrid distributed throughout the Atlantic Ocean, Mediterranean and Black Seas. This migratory predator represents an important fishery resource along its range of distribution, as well as in the NW Mediterranean. However, despite its commercial and ecological importance, accurate information of its trophic habits in the Mediterranean is very scarce. In this study, our main aim is to examine the feeding ecology (diet composition and trophic level) of the Atlantic bonito in the NW Mediterranean Sea by combining stable isotopic and stomach content methodologies at different temporal scales. Also we compare the trophic habits of the Atlantic bonito with information from several species of the same ecosystem to determine its ecological role. Our stable isotopic and stomach content results reveal a clearly importance of small pelagic fish in the diet of this top predator without seasonal changes in diet during the year. In particular, the diet of the Atlantic bonito includes the European anchovy Engraulis encrasicolus as the main prey in its diet. Other pelagic species found in its diet are the European pilchard Sardina pilchardus and the round sardinella Sardinella aurita. These results indicate the position of this species as an important predator within the pelagic food web of the NW Mediterranean Sea and highlight that the Atlantic bonito feeds on pelagic species that are ecologically and commercially very important in the area. In addition, comparing the trophic position of the Atlantic bonito with other species of the study area, we observe that this species shows a similar position as other important predators such as bluefin tuna, other tunids, and Audouin’s gullPeer Reviewe