Krzysztof W. Opaliński2 and Piotr
1 Sea Fisheries Institute, Kołłątaja 1, 81-332 Gdynia, Poland
2 Institute of Ecology, Polish Academy of Sciences, 05-150 Łomianki, Poland
Key words: Osmerus eperlanus, food ration, Vistula Lagoon
To estimate the influence of the smelt Osmerus eperlanus (L.) on the zooplankton in the Vistula Lagoon the consumption rate of this fish was calculated. The direct method for estimating production P, respiration R and egestion F was used. The daily fish food ration C was calculated as the sum of the above parameters of the energy butget: C = P + R + F + U. The energy budget of smelt weighing 7.6 mg dry weight (90.2 mg wet wt.) at the natural environmental temperature (17.5�C) is as follows (in cal per mg dry wt of fish per day): C (2.51 cal) = P (1.12 cal) + R (0.48 cal) + F (0.75 cal) + U (0.16 cal). The daily food ration of smelt larvae is thus 4.02 mg dry wt of zooplankton per individual (0.53 mg dry wt of zooplankton per mg dry wt of fish).