Feeding strategy of Downs herring larvae in the English Channel and North Sea

The aim of this study was to characterize the feeding strategy of Downs herring larvae at critical period during winter in the English Channel and North Sea was defined to assess whether nutrition is responsible for low recruitment in stocks over the past years. Data collected during the French part of the International Bottom Trawl Survey from 2008 to 2014 were used to analyse fish larvae diet by direct observation using Scanning Electron Microscope (SEM). Gut content methods generally used for copepods was adapted to fish larvae to assess phytoplankton ingestion. The relative importance of small preys (0,5-375µm) observed in gut contents proved the essential role of SEM to better acknowledge Downs herring diet. We demonstrated that Downs herring larvae from 6 to 20 mm were omnivorous, specialized on invertebrate eggs and more rarely consumed a variety of phytoplankton and zooplankton prey. They also seemed to positively select rare phytoplankton prey whereas they negatively select several zooplankton prey.