Species composition, growth, and food consumption of age-0 fish were investigated in a brackish inlet of the Baltic. Fish larvae and juveniles were caught both in on- and offshore areas using a mini-bongo net and dip nets once a week between April and June in 1990 and 1991. Additionally, the succession of the zooplankton community was regularly observed.

Herring (Clupea harengus) and perch (Perca fluviatilis) were the dominant fish species. Their diet nearly exclusively consisted of nauplii, copepodite stages, and adults of the most abundant copepod species Eurytemora affinis. The uptake of larger prey, especially the mysid Neomysis integer, increased with length of fish. Growth rate of both species was estimated to be very high in comparison to values measured in other waters.

Distribution of fish was determined by salinity, water depth, and macrophyte cover of the bottom. Whereas the 0+ herring and gobies (Pomatoschistus sp.) were pelagic and preferred areas with about 4 - 6 ppt salinity, young roach (Rutilus rutilus) were more abundant in littoral areas with lower salinity. During its first weeks of life, age-0 perch fed in open water, but at about 25 mm total length they changed their habitat to areas with low water depth.

Calculating daily food consumption of fish by bioenergetics models (Kitchell et al., Vinberg, Kerr & Dickie) and by direct measurement during 24 hours, it was found that ingestion of prey species never exceeded the daily production rate of the zooplankton. Consequently, it was concluded that the predation influence of age-0 fish on the population collapse of E.affinis yearly observed in late spring was negligible. Additionally, competition for food was assumed to be not a structuring factor within the community of 0+ fish species.