Small pelagic fish (SPF), i.e. those inhabiting the water column, are difficult to study in shallow coastal systems such as the Wadden Sea. Yet, they make up a substantial part of the overall fish biomass and play key ecological roles. Using a combination of traditional and new methods, we studied the function of the Wadden Sea for SPF and their role in the food web. We found that the Wadden Sea primarily serves as a nursery for juvenile SPF. Diet analysis revealed an opportunistic, seasonally varied diet, including copepods and (larvae of) benthic species, which facilitates energy transfer between benthic and pelagic habitats. Focusing on their role as prey, we found that common tern distribution and foraging preferences largely overlapped with SPF distribution and sizes. This thesis underscores the essential roles of SPF in coastal ecosystems and their vast abundance in the murky, shallow waters of the Wadden Sea.