Twenty largemouth bass (Micropterus salmoides) , 10 containing dummy radio transmitters and 10 control, were studied in hatchery ponds to determine the effects of implanted transmitters on swimming, feeding, spawning and catchability behavior. Eight additional bass were subjected to buoyancy compensation tests under laboratory conditions. Pond studies indicated no significant difference in swimming movement or catchability between transmitter and control bass. Both transmitter and control bass were observed feeding and spawning. All transmitters were encapsulated in a skin-like sac within the body cavity at study termination. Laboratory experiments indicated the negative buoyancy of the transmitters affected bass temporarily, and fin beats increased only during the time it took bass to adjust to the effect of the transmitter.