English: Grey Seal food web in the Baltic Sea. The classifications denote which role each species/food web component has in the tested statistical models. Grey Seal is the most abundant seal species in the Baltic Sea and feed mainly on sprat, herring and cod. Cod is the predominant piscivorous fish in many parts of the region, feeding mainly on sprat and herring, which together constitute around 85% of the pelagic fish species in terms of biomass. Cod also feeds on benthic invertebrates, in particular the isopod Saduria entomon. Sprat of all sizes are zooplanktivorous, whereas larger herring also feeds on benthic species. In particular, the lipid-rich amphipod Monoporeia affinis can constitute a large proportion of the herring diet. S. entomon feeds mainly on M. affinis; in the Bothnian Sea, they form a tightly coupled predator–prey system. Polychaetes contribute to the diet of herring and S. entomon to a smaller extent (not shown in this figure)