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Consumption of fish eggs is a major component of the trophodynamics of several marine ecosys)tems. Nevertheless, demonstrating the consumption by stomach content analysis is complex, notably due to the high digestibility of eggs. Atlantic herring (Clupea harengus) of the Downs substock migrate from the North Sea to spawn in the Eastern English Channel during winter. On the basis of an opportunistic sampling of 5 red mul)lets (Mullus surmuletus) displaying herring eggs in their stomachs, this paper was the opportunity to document for the first time the trophic importance of herring eggs in the English Channel, by combining automated analy- sis of prey images with stable isotope and C:N ratios measurement. Eggs represented more than 90% of the prey items observed in the stomachs. In addition, low δ13C and high δ15N andC:N ratios demonstrated that this obser- vation does not reflect occasional consumption of eggs, but that eggs are a common prey all through the entire spawning season. Automated image analysis demonstrated efficiency to produce semi-quantitative indicators of the diet, but manual post processing should be implemented if accuracy is needed. This work was nevertheless the opportunity to start the development of a learning set adapted to benthic organisms and available for further similar applications. This work also demonstrated the importance of a holistic approach of trophic interactions to manage exploited species. [ABSTRACT FROM AUTHOR]

Les signalements opportunistes, notamment pour les espèces rares, sont souvent les premières données disponibles révélant des expansions géographiques dans un contexte de changement global des écosystèmes marins. Sur la base d'un premier signalement au nord de la mer du Nord du poisson mésopélagique Diretmichthys parini (Post et Quéro, 1981), initialement décrit comme tropical et subtropical, une hypothèse d'expansion géographique en relation avec le réchauffement climatique a été formulée en 2017. L'analyse d'un plus grand jeu de données spatiales et temporelles, incluant notamment des signalements anciens (1992-2016) en Islande et récents en Norvège (2015-2017), induit la révision de cette hypothèse et permet de reconsidérer les préférences thermiques des adultes de cette espèce. Ce travail illustre également l'importance de prendre en compte les réseaux sociaux pour suivre les signalements opportunistes, car la surprise liée à la capture de ces poissons inhabituels y entraîne souvent la publication des photos par le grand public. [ABSTRACT FROM AUTHOR]

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Artificial reefs are classical tools used in coastal zones to sustain small-scale fisheries. In the Bay of Marseilles, the largest Mediterranean artificial reef system was deployed for this purpose. This system offers a valuable opportunity to better understand the trophic functioning of artificial reefs. This implies to (1) characterize the organic matter (OM) sources, (2) determine how they are used by low trophic level consumers, and (3) follow their fate in the trophic networks. All these issues were assessed by three coupled methodological approaches. Carbon and nitrogen stable isotope ratios are a powerful tool, classically used to follow OM sources through trophic networks. Their biochemical composition (carbohydrate, lipid and protein contents) would bring data on their potential nutritional qualities for consumers. Finally, stomach content analyses allow explaining the trophic position of fishes living on the artificial reefs and their variations. OM sources display isotopic and biochemical differences reflecting their particular composition and functioning. Suspended particulate OM (POM) is highly variable, under the influence of marine and terrestrial inputs, and controlled by climatic forcing. POM, selectively used by filter-feeder invertebrates, dominant on artificial reefs, represents the main source of carbon of the artificial reef food webs. The benthic primary production is heterogeneous isotopically and biochemically, and exhibits mainly high insoluble carbohydrates contents. Benthic primary production is integrated into trophic networks mainly in the form of detritus, while its direct consumption is limited. Eventually, the sediment organic matter is a detrital pool, characterized by a low variability and a poor nutritional quality. Artificial reefs do not appear to modify the organization and the functioning of natural fish communities, and provide them diversified and important food resources. Stable isotope and stomach content analyses confirm the consumption of artificial reef invertebrates by small carnivorous fishes, preyed themselves by piscivorous species. All these results confirm that artificial reefs can efficiently increase fish biomasses by local production based on phytoplanktonic and local benthic OM sources. [ABSTRACT FROM AUTHOR]