Abstract The influence of induced negative buoyancy on depth distribution, pectoral fin movements, and gas secretion was observed for bluegills of ca. 130 g weight. Negative buoyancy was induced by inserting small weights (excess mass = 2.76 g) into the fish's stomach. Sham handled and minimally handled fish were compared with weighted fish. Initially weighted fish sank to the bottom and in a 160-cm deep tank, most remained there for 4 hr; in a 45-cm deep aquarium, most fish left the bottom in 1.5 hr. Pectoral fin movements (median number/min) of fish hovering in midwater increased from 48 to 104 when weights were added. As fish regained neutral buoyancy by gas secretion, time spent on the bottom and pectoral fin movements returned to pretreatment levels. Gas was secreted to the gas bladder of weighted fish at a maximum rate of approximately 0.1 ml/kg of fish/min at 21 C, such that fish in 30-cm deep aquaria could regain neutral buoyancy within 300 min after weight injection. The influence of induced nega...