Fiches pratiques d’aide à l'identification des espèces marines de Méditerranée occidentale. Campagnes halieutiques

Ces fiches sur des espèces marines de Méditerranée occidentale sont des documents de terrain d’aide à l'identification. Elles sont principalement établies pour favoriser la qualité et la rapidité d’identification des espèces capturées lors des campagnes halieutiques en Méditerranée. Ces fiches sont donc destinées à des opérateurs avertis. Sans être exhaustif, le domaine couvert par ces fiches correspond à plus de 300 espèces (version 4) de Poissons, Céphalopodes et Crustacés. Ces espèces sont soit pêchées lors des campagnes de chalutages du Golfe du Lion et de l’Est-Corse (à des profondeurs comprises entre 20 à 800 m), soit susceptibles de l’être car référencées/signalées dans la zone. Une fiche regroupe des espèces similaires, leurs principales caractéristiques, et lorsque qu’il existe des possibilités de confusion, présentent les principaux critères discriminants. Ces fiches ne constituent donc pas un manuel d’identification faunistique. L’expérience 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 prélèvements des otolithes chez les grands pélagiques

Ce guide présente les modes et règles de prélèvement puis de stockage des otolithes de grands pélagiques (thons et espadons). Ils ont été 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 réseaux de surveillance coordonnés au niveau international, en particulier au sein du règlement européen sur la collecte des données halieutiques (DCMAP, Data Collection Multi Annual Programme). Ce guide a pour but de standardiser les prélèvements d’otolithes effectués à l'Ifremer sur ces grands pélagiques. Il reprend et complète la synthèse française des procédures d'estimation d'âge (Mahé et al., 2009), le manuel d'utilisation du fichier : "Parametres biologiques v7.xls" (Mahé et al., 2007) et le guide de prélèvement des pièces calcifiées (Mahé 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 (ä15N, ä13C) analyses were performed, and the main factors explaining variations in ä15N 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 pesquerías mediterráneas. Este estudio se centra en la ecología alimentaria de juveniles y adultos de merluza en el Golfo de León, utilizando información de campañas científicas llevadas a cabo en primavera y otoño durante tres años (2004-2006). Se realizaron análisis de contenidos estomacales e isótopos estables (δ15N, δ13C), mientras que la identificación de los principales factores que explican las variaciones en δ15N se investigaron utilizando GLMs. En el Golfo de León, la merluza se alimenta mayoritariamente de crustáceos y peces y alcanzan un régimen piscívoro dominante a los 15 cm TL. Los peces pelágicos (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 también muestran que la talla y la diversidad de las presas varían entre distintas clases de talla de la merluza, probablemente como resultado de una distribución espacial diferente y/o migraciones en busca de alimento. Finalmente, este estudio postula que la proporción de sexos desequilibrada (80% de hembras frente a 20% de machos) que se observa en estado adulto podría estar relacionada con la combinación de diferentes patrones de crecimiento, dieta y tasa de explotación en la plataforma continental, donde los machos pasan un mayor período 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 organisms’ 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 espèces démersales et benthiques : Rapport final de l’action 3 du Projet GOLDYS

De façon à obtenir une meilleure compréhension des cycles de vie, répartitions spatiales et dynamiques des populations exploitées, des campagnes scientifiques (reprenant le protocole des campagnes MEDITS) ont été déployées en 2022-2023. Elles visaient à d’obtenir un suivi saisonnier de la ressource (en particulier, répartitions spatiales des juvéniles et des reproducteurs). Les objectifs visés étaient : 1) une évaluation de la biodiversité (inventaire, structure et répartition spatiale des assemblages) et des successions saisonnières des communautés d’invertébrés benthiques et ichtyologiques observées sur un an ; 2) pour un certain nombre d’espèces, obtenir des informations détaillées sur leur cycle de vie dans la zone d’étude ; 3) produire des cartes saisonnières des principales espèces rencontrées par stade de vie (juvéniles et adultes) de façon à obtenir un premier aperçu de leurs dynamiques saisonnières sur un an. Le suivi de la distribution des principales espèces rencontrées a permis d’obtenir un premier aperçu de leurs dynamiques saisonnières sur un an. Les résultats obtenus ici indiquent que les assemblages sont fortement structurés par le gradient bathymétrique et pour beaucoup d’espèces, les distributions sont assez stables sur l’ensemble de l’année. Il est probable que les observations estivales obtenues lors de la campagne récurrente MEDITS soient suffisamment représentatives dans un grand nombre de cas. La définition de la taille médiane à première maturité a permis de distinguer plus précisément les juvéniles des adultes et de comparer leurs distributions saisonnières

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 δ15N values and high proportions of mono-unsaturated fatty acids). The trophic position of YFT decreased slightly in the last 15 years (δ15N values decrease ~0.5 ⠰) 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 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 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 60 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