Behavior of Sandeels Feeding on Herring Larvae

It is a common problem in ecosystem studies that information about predation on fish larvae is extremely sparse. There is little information about agents of mortality. This is likely to be because fish larvae are digested very rapidly in a predator’s stomach. This study describes controlled experiments designed to evaluate the potential role of small low-trophic level fishes as predators on pelagic fish larvae. The study shows that sandeels, Ammodytes marinus, prefer herring larvae to copepods, their normal food items. When herring larvae are available the sandeels change behavior, their swimming speed increases drastically, and copepods are almost totally excluded from the diet. Once eaten, the herring larvae are only identifiable in the sandeel guts for 15-30 minutes using morphological criteria. It is concluded that abundant low-trophic level fishes potentially may have considerable impact on other fish species, even those that are normally not assumed to be predators on the low-trophic level fishes themselves.