Influence of external transmitter shape and size on tag retention and growth of juvenile lake sturgeon

Few studies have examined the effects of external radio transmitters on small fish. We evaluated the influence of two shapes (cylindrical and compressed) and three sizes (small, medium, and large [approximately 1.25, 2.00, and 6.00% of body weight, respectively]) of dummy transmitters on the tag retention and growth of juvenile lake sturgeon Acipenser fulvescens in an 8-week laboratory experiment. Thirty-five lake sturgeon were contained in each of three tanks, with five fish in each tank assigned to each of the six transmitter treatments. The remaining five fish in each tank, which served as the control group, were handled but did not receive a transmitter. A greater number of compressed transmitters were shed than cylindrical transmitters, and more large transmitters were lost than small or medium transmitters. Fish with medium and large transmitters, regardless of shape, exhibited lower growth than fish with small transmitters or the control group from week 2 through the end of the study. Only fish with small transmitters exhibited growth similar to that of the control group. Our results suggest that external radio transmitters should not exceed 1.25% of body weight and should be cylindrical in shape for telemetry studies involving juvenile lake sturgeon.