19 research outputs found
Fiches pratiques dâaide Ă l'identification des espĂšces marines de MĂ©diterranĂ©e occidentale. Campagnes halieutiques
Ces fiches sur des espĂšces marines de MĂ©diterranĂ©e occidentale sont des documents de terrain dâaide Ă l'identification. Elles sont principalement Ă©tablies pour favoriser la qualitĂ© et la rapiditĂ© dâidentification des espĂšces capturĂ©es lors des campagnes halieutiques en MĂ©diterranĂ©e. Ces fiches sont donc destinĂ©es Ă des opĂ©rateurs avertis. Sans ĂȘtre exhaustif, le domaine couvert par ces fiches correspond Ă plus de 300 espĂšces (version 4) de Poissons, CĂ©phalopodes et CrustacĂ©s. Ces espĂšces sont soit pĂȘchĂ©es lors des campagnes de chalutages du Golfe du Lion et de lâEst-Corse (Ă des profondeurs comprises entre 20 Ă 800 m), soit susceptibles de lâĂȘtre car rĂ©fĂ©rencĂ©es/signalĂ©es dans la zone. Une fiche regroupe des espĂšces similaires, leurs principales caractĂ©ristiques, et lorsque quâil existe des possibilitĂ©s de confusion, prĂ©sentent les principaux critĂšres discriminants. Ces fiches ne constituent donc pas un manuel dâidentification faunistique. LâexpĂ©rience et le savoir-faire de nombreux intervenants ont permis la constitution de ces fiches, quel que soit leur niveau de contribution, nous les en remercions tous
Metabarcoding confirms the opportunistic foraging behaviour of Atlantic bluefin tuna and reveals the importance of gelatinous prey
WOS:000685100200001International audienceStudies of the diet, feeding habits and trophic activity of top marine predators are essential for understanding their trophodynamics. The main direct method used for such studies thus far has been morphological inventories of stomach contents. This approach presents limitations such as missing gelatinous prey, which are usually digested too quickly to be detectable. Here, we analysed the stomachs of 48 Atlantic bluefin tuna (Thunnus thynnus, approximately 15 to 60 kg, including juveniles and adult fishes) collected from the Mediterranean Sea through the metabarcoding of two gene regions (cytochrome c oxidase subunit I (COI) and the ribosomal 18S-V1V2 region). The identified prey taxa and their relative read abundances (RRAs) estimated using COI results were in line with the findings of morphologically based inventories simultaneously performed on the same set of tuna samples. In both cases (and with the same rankings), the prey taxa included anchovy (Engraulis encrasicolus, here detected in more than 80% of samples, RRA = 43%), sardine (Sardina pilchardus, also approximately 80%, RRA = 30%), sprat (Sprattus sprattus, approximately 66%, RRA = 8%), mackerel (Scomber colias, approximately 44%, RRA = 7%) and cephalopods (approximately 15%, RRA = 1.4%). Another striking result was the detection, based on 18S (with which vertebrates were detected as the most abundant group, RRA = 61.6%), of a high prevalence and diversity of gelatinous organisms (RRA = 27.1%), including cnidarians (6.7%), salps (11.7%), and ctenophores (8.7%), the latter increasing with the size of the predator. These results thus support the hypothesis of the role of gelatinous prey in the diet of Atlantic bluefin tuna, suggesting that this species is even more generalist and opportunistic than previously thought. This study further confirms that DNA metabarcoding can be a powerful tool for assessing the diet and trophodynamics of top marine predators
Guide de prélÚvements des otolithes chez les grands pélagiques
Ce guide prĂ©sente les modes et rĂšgles de prĂ©lĂšvement puis de stockage des otolithes de grands pĂ©lagiques (thons et espadons). Ils ont Ă©tĂ© mis en place dans le cadre de projets de recherche comme « Germon » (http://wwz.ifremer.fr/lareunion/Les-projets/GERMON-en-cours), « IOSSS-Espadon » (http://wwz.ifremer.fr/lareunion/Les-projets/IOSSS-ESPADON) et «thon rouge (ICCAT-GBYP) » et dans le cadre de rĂ©seaux de surveillance coordonnĂ©s au niveau international, en particulier au sein du rĂšglement europĂ©en sur la collecte des donnĂ©es halieutiques (DCMAP, Data Collection Multi Annual Programme). Ce guide a pour but de standardiser les prĂ©lĂšvements dâotolithes effectuĂ©s Ă l'Ifremer sur ces grands pĂ©lagiques. Il reprend et complĂšte la synthĂšse française des procĂ©dures d'estimation d'Ăąge (MahĂ© et al., 2009), le manuel d'utilisation du fichier : "Parametres biologiques v7.xls" (MahĂ© et al., 2007) et le guide de prĂ©lĂšvement des piĂšces calcifiĂ©es (MahĂ© et al., 2013)
Trophic ecology of the European Hake in the Gulf of Lions, Northwestern Mediterranean Sea
The European hake, Merluccius merluccius, is an important resource for Mediterranean fisheries. This study focuses on juvenile and adult hake feeding ecology in the Gulf of Lions, using information from scientific surveys carried out during two seasons and three years (2004-2006). Stomach content and stable isotope (Ă€15N, Ă€13C) analyses were performed, and the main factors explaining variations in Ă€15N were investigated using GLMs. In the Gulf of Lions, hake mostly fed on crustaceans and fish and a dominant piscivorous regime was reached at 15 cm total length. Pelagic fish (sardine, anchovy and small blue whiting) were the main source of prey (40%-80%) and cannibalism was low (<5%). The results confirmed that hake is an opportunistic feeder and also showed that the size and diversity of prey vary among hake size classes, probably as a result of the different spatial distribution and/or foraging migrations. The present study finally postulates that the unbalanced sex ratio (80% female against 20% male) observed at the adult stage could be related to the combination of growth pattern differences, diet and exploitation rate on the continental shelf, where the males spend a longer period of time.La merluza europea, Merluccius merluccius, es un importante recurso para las pesquerĂas mediterrĂĄneas. Este estudio se centra en la ecologĂa alimentaria de juveniles y adultos de merluza en el Golfo de LeĂłn, utilizando informaciĂłn de campañas cientĂficas llevadas a cabo en primavera y otoño durante tres años (2004-2006). Se realizaron anĂĄlisis de contenidos estomacales e isĂłtopos estables (ÎŽ15N, ÎŽ13C), mientras que la identificaciĂłn de los principales factores que explican las variaciones en ÎŽ15N se investigaron utilizando GLMs. En el Golfo de LeĂłn, la merluza se alimenta mayoritariamente de crustĂĄceos y peces y alcanzan un rĂ©gimen piscĂvoro dominante a los 15 cm TL. Los peces pelĂĄgicos (sardina, anchoa y bacaladilla pequeña) constituyen el mayor porcentaje de sus presas (40-80%) y el canibalismo es bajo (<5%). Los resultados confirman que la merluza es un alimentador oportunista y tambiĂ©n muestran que la talla y la diversidad de las presas varĂan entre distintas clases de talla de la merluza, probablemente como resultado de una distribuciĂłn espacial diferente y/o migraciones en busca de alimento. Finalmente, este estudio postula que la proporciĂłn de sexos desequilibrada (80% de hembras frente a 20% de machos) que se observa en estado adulto podrĂa estar relacionada con la combinaciĂłn de diferentes patrones de crecimiento, dieta y tasa de explotaciĂłn en la plataforma continental, donde los machos pasan un mayor perĂodo de tiempo
Molecular fingerprint of gilthead seabream physiology in response to pollutant mixtures in the wild
The increase in trace element concentrations in the aquatic environment due to anthropogenic activities, urge the need for their monitoring and their potential toxicity, chronic persistence, bioaccumulation, and biomagnification at different trophic levels. Gilthead seabream is a species of commercial importance in the Mediterranean Sea, both for the aquaculture and fisheries sectors, however very little is known about their trace element contamination and the resulting effect on their health. In the present study, 135 juveniles were collected from seven coastal lagoons known to be essential nursery areas for this species. Our results revealed the accumulation of multiple trace elements in individuals and distinct contamination signatures between lagoons which might lead to contrasted quality as nurseries for juveniles of numerous highly prized fish species in addition to seabreams. We further evaluated the potential adverse effect of these complex contamination mixtures on the liver (the main organ implicated in the metabolism of xenobiotics) and red muscle (a highly metabolic organ) using a proteomic approach. Alteration in cellular organization pathways and protein transport were detected in both tissues (albeit they were not similarly regulated). Chromosome organization and telomere maintenance in liver appeared to be affected by contaminant mixture which could increase mortality, age-related disease risk and shorter lifetime expectancy for these juveniles. Red muscle proteome also demonstrated an upregulation of pathways involved in metabolism in response to contamination which raise the issue of potential energy allocation trade-offs between the organismsâ main functions such as reproduction and growth. This study provides new insights into the cellular and molecular responses of seabreams to environmental pollution and proposed biomarkers of health effects of trace element that could serve as a starting point for larger-scale biomonitoring programs
Seasonal habitat and length influence on the trophic niche of co-occurring tropical tunas in the eastern Atlantic Ocean
International audienceIn the Gulf of Guinea, bigeye tuna (Thunnus obesus; BET) and yellowfin tuna (Thunnus albacares; YFT) are an important part of commercial fisheries and play a prominent ecological role as top predators. Using fatty acid profiles and carbon and nitrogen stable isotopes, we examined their trophic niche partitioning in this understudied region. Trophic niche overlap was high (> 70%), similar to percentages in other ocean basins. BET occupied a higher trophic position than YFT and fed on deeper prey (high delta N-15 values and high proportions of monounsaturated fatty acids). The trophic position of YFT decreased slightly in the last 15 years (delta N-15 values decreased by similar to 0.5 parts per thousand), suggesting a change in epipelagic communities, as observed in the eastern Pacific Ocean. Ontogenic changes were limited to BET. For both species, the dietary proportion of the diatom marker 20:5(n-3) increased in the seasonal upwelling area, highlighting the influence of seasonal habitat on the diet of tuna. The relatively lipid-rich muscle (similar to 6% dry mass) of Atlantic tropical tuna suggests a richer diet in this region than that of Indian Ocean tropical tuna and (or) differences in energy allocation strategies
Suivi spatio-temporel des espĂšces dĂ©mersales et benthiques : Rapport final de lâaction 3 du Projet GOLDYS
De façon Ă obtenir une meilleure comprĂ©hension des cycles de vie, rĂ©partitions spatiales et dynamiques des populations exploitĂ©es, des campagnes scientifiques (reprenant le protocole des campagnes MEDITS) ont Ă©tĂ© dĂ©ployĂ©es en 2022-2023. Elles visaient Ă dâobtenir un suivi saisonnier de la ressource (en particulier, rĂ©partitions spatiales des juvĂ©niles et des reproducteurs). Les objectifs visĂ©s Ă©taient : 1) une Ă©valuation de la biodiversitĂ© (inventaire, structure et rĂ©partition spatiale des assemblages) et des successions saisonniĂšres des communautĂ©s dâinvertĂ©brĂ©s benthiques et ichtyologiques observĂ©es sur un an ; 2) pour un certain nombre dâespĂšces, obtenir des informations dĂ©taillĂ©es sur leur cycle de vie dans la zone dâĂ©tude ; 3) produire des cartes saisonniĂšres des principales espĂšces rencontrĂ©es par stade de vie (juvĂ©niles et adultes) de façon Ă obtenir un premier aperçu de leurs dynamiques saisonniĂšres sur un an. Le suivi de la distribution des principales espĂšces rencontrĂ©es a permis dâobtenir un premier aperçu de leurs dynamiques saisonniĂšres sur un an. Les rĂ©sultats obtenus ici indiquent que les assemblages sont fortement structurĂ©s par le gradient bathymĂ©trique et pour beaucoup dâespĂšces, les distributions sont assez stables sur lâensemble de lâannĂ©e. Il est probable que les observations estivales obtenues lors de la campagne rĂ©currente MEDITS soient suffisamment reprĂ©sentatives dans un grand nombre de cas. La dĂ©finition de la taille mĂ©diane Ă premiĂšre maturitĂ© a permis de distinguer plus prĂ©cisĂ©ment les juvĂ©niles des adultes et de comparer leurs distributions saisonniĂšres
Seasonal habitat and length influence on the trophic niche of co-occurring tropical tunas in the eastern Atlantic Ocean
In the Gulf of Guinea, bigeye Thunnus obesus (BET) and yellowfin tuna Thunnus albacares (YFT) are important for commercial fisheries and play a prominent ecological role as top predators. Using fatty acid profiles and carbon and nitrogen stable isotopes we examined their niche partitioning in this understudied region. Niche overlap was high (>70%), similar to percentages in other ocean basins. BET occupied a higher trophic position than YFT and fed on deeper prey (high ĂÂŽ15N values and high proportions of mono-unsaturated fatty acids). The trophic position of YFT decreased slightly in the last 15 years (ĂÂŽ15N values decrease ~0.5 Ăą °) suggesting a change in epipelagic communities, as observed in the eastern Pacific Ocean. Ontogenic changes were limited to BET. For both species, the dietary proportion of the diatoms marker (20:5n-3) increased in the seasonal upwelling area, highlighting the seasonal habitat influence on tunas diet. The relatively lipid-rich muscle (~6 % dry weight) of Atlantic tropical tunas suggested a richer diet in this region than for Indian Ocean tropical tunas and/or differences in energy allocation strategies.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
Temperature-dependent metabolic consequences of food deprivation in the European sardine
International audienceAquatic ecosystems can exhibit seasonal variation in resource availability and animals have evolved to cope with the associated caloric restriction. During winter in the NW Mediterranean Sea, the European sardine Sardina pilchardus naturally experiences caloric restriction owing to a decrease in the diversity and quantity of plankton. However, ongoing global warming has had deleterious effects on plankton communities such that food shortages may occur throughout the year, especially under warm conditions in the summer. We investigated the interactive effects of temperature and food availability on sardine metabolism by continuously monitoring whole-animal respiration of groups of control (fed) and food-deprived sardines over a 60-day experiment in winter (12°C) or summer (20°C) conditions under natural photoperiod. In addition, we measured mitochondrial respiration of red muscle fibres, biometric variables and energy reserves of individuals sampled at 30 and 60â
days. This revealed that winter food deprivation elicits energy saving mechanisms at whole animal and cellular levels by maintaining a low metabolism to preserve energy reserves, allowing high levels of survival. By contrast, despite energy saving mechanisms at the mitochondrial level, whole animal metabolic rate was high during food deprivation in summer, causing increased consumption of energy reserves at the muscular level and high mortality after 60â
days. Furthermore, a 5-day re-feeding did not improve survival, and mortalities continued, suggesting that long-term food deprivation at high temperatures causes profound stress in sardines that potentially impairs nutrient absorption
Temperature-dependent metabolic consequences of food deprivation in the European sardine
Aquatic ecosystems can exhibit seasonal variation in resource availability and animals have evolved to cope with the associated caloric restriction. During winter in the NW Mediterranean Sea, the European sardine Sardina pilchardus naturally experiences caloric restriction due to a decrease in diversity and quantity of plankton. Ongoing global warming has, however, had deleterious effects on plankton communities such that food shortages may occur throughout the year, especially under warm conditions in the summer. We investigated the interactive effects of temperature and food availability on sardine metabolism, by continuously monitoring whole-animal respiration of groups of control (fed) and food-deprived sardines over a 60-day experiment in winter (12°C) or summer (20°C) conditions under natural photoperiod. In addition, we measured mitochondrial respiration of red muscle fibres, biometric variables and energy reserves, of individuals sampled at 30 and 60 days. This revealed that winter food deprivation elicits energy saving mechanisms at whole animal and cellular levels by maintaining a low metabolism to preserve energy reserves, allowing high survival. By contrast, despite energy saving mechanisms at the mitochondrial level, whole animal metabolic rate was high during food deprivation in summer, causing increased consumption of energy reserves at the muscular level and high mortality after 60 days. Furthermore, a 5-day refeeding did not improve survival and mortalities actually continued, suggesting that long-term food deprivation at high temperatures caused profound stress in sardines that potentially impaired nutrient absorption