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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]

Parasites play a key but overlooked role in the functioning of marine systems. Understanding the drivers of parasite infection in fish is thus crucial. Anisakis levels in the Atlantic horse mackerel Trachurus trachurus resulted from both biotic and environmental drivers. Ontogenic variation of the diet was the first driver of Anisakis level. The nonlinear pattern confirmed that the variation in parasitism was related to ontogenetic dietary shifts. The impact of depth on diet also explained the effect of depth on parasites. In deeper areas, fish only access pelagic prey, where Anisakis presence is high, consistent with the pelagic nature of the parasite. Finally, relative proportions of parasitic burden by tissue appeared to be driven by lipid content. In lipid-rich species like T. trachurus, Anisakis can find favorable conditions in the body cavity and in muscle and avoid the liver. Parasitism levels in fish are thus the result of patterns at play at different levels, and these factors should be better considered before being able to include parasites in an integrated vision of marine ecosystem functioning. [ABSTRACT FROM AUTHOR]