MIGRATORY BEHAVIOR OF YOUNG STURGEON, ACIPENSER OXYRINCHUS MITCHILL, IN THE ODER RIVER DRAINAGE. PRELIMINARY RESULTS OF A RADIO TELEMETRIC STUDY IN THE DRAWA RIVER, POLAND
Frank Fredrich*, Andrzej Kapusta**, Markus Ebert***, Arkadiusz Duda**, Jörn Gessner***
*Society to Save the Sturgeon e.V., Rostock, Germany
**Department of Ichthyology, The Stanisław Sakowicz Inland Fisheries Institute in Olsztyn, Poland
***Department of Biology and Ecology of Fishes, Institute of Freshwater Ecology and Inland Fishery, Berlin, Germany
ABSTRACT. The movements of individual juvenile sturgeon, Acipenser oxyrinchus Mitchill, during their first stage of downstream migration were observed in the Drawa River, Poland. Two groups of 10 sturgeon each (9 months old, reared in closed recirculation systems) were tagged with internal radio-transmitters. The first group of sturgeon (119-184 g) were tagged with Holohill BD-2N transmitters (weight 0.43 g, operational life 14d) and released on May 7. Fish from the second group (143-206 g) were tagged with BD-2 (weight 1.2 g, operational life 56d) and were released on May 24. The releases took place in the Drawa River below Kamienna Dam, 33 km upstream from the river’s confluence with the Noteć River. All of the fish moved downstream, but migration speeds differed. Seven sturgeon from the first group reached the confluence with the Noteć River, approximately 30 km downstream from the release site, during the first 18 days, which indicated there had been staging intervals in pools. Within four days, six fish from the second group had moved downstream the Drawa River and were located 20 km downstream from the confluence with the Noteć River. The downstream migration speed of the fish correlated with fish size and increased with water temperature.
Key words: MOVEMENT, INDIVIDUAL BEHAVIOR, HABITAT, STURGEONS