INFLUENCE OF TRANSMITTER ATTACHMENT PROCEDURES ON SWIMMING PERFORMANCE OF WILD AND HATCHERY-REARED ATLANTIC SALMON SMOLTS

Effects of transmitter attachment procedures on smelts of Atlantic sal mon Salmo salar have primarily been examined in the laboratory with ha tchery-reared fish. Biotelemetry researchers must extrapolate findings of tagging studies to wild, migrating smelts. Because hatchery rearin g can affect salmonid development and because field tagging procedures and environmental conditions can differ from those in the laboratory, we measured critical swimming speed of hatchery-reared Atlantic salmo n smelts equipped with internal, external, or gastric dummy radio tran smitters in the laboratory. We then repeated the experiment with wild, migrating fish in ambient environmental conditions. Swimming ability of hatchery smelts was not significantly affected by any attachment pr ocedure, and no significant differences were found between fish tested 1 or 16 h after tagging. Similarly, wild smelts were not impaired by gastric transmitters; however, performance of wild fish tested 1 or 16 h after internal or external attachment was significantly lower than that of wild controls. Thus, reaction of hatchery-reared Atlantic salm on smelts to attachment procedures can differ from that of wild migran ts. Biotelemetry researchers should exercise caution in interpreting d ata obtained from wild Atlantic salmon smelts equipped with internal o r external radio transmitters during the first 16 h after tagging.