Sea Fisheries Institute, Kołłątaja 1, 81-332 Gdynia, Poland
Key words: smelt, feeding, fish larvae, predation, Vistula Lagoon
Investigations of the occurrence and species composition of fish larvae in smelt Osmerus eperlanus (L.) food were based on the analysis of the stomach contents of 365 and 1,240 specimens from age group 1 which were caught in April-June 1998 and 1999. The frequency that fish larvae occurred in smelt food (%F) increased with predator length, and it varied, on average, from 9.6% in 1998 to 4.7% in 1999. The length of the prey varied from 3.5-30 mm to 3.7-24.6 mm in 1998 and 1999, respectively. However, their species structure was different; in the majority of cases in 1998 prey consisted of the larvae and fry of percid fish (72.5%) and smelt (21.6%), while in 1999, herring larvae dominated (86.4%). The results of investigations of smelt food indicate that this fish has a rather insignificant role as a predator. The influence of smelt age group 1 on the mortality of herring larvae, which occur on a massive scale in spring in the Vistula Lagoon, is minimal and concerns only the early larvae developmental period, i.e. the yolk-sac stage.