Adjustment of Buoyancy by Tadpole Madtom, Noturus gyrinus, and Black Bullhead, Ictalurus melas, in Response to a Change in Water Velocity

Abstract

Tadopole madtom (Noturus gyrinus) and black bullhead (Ictalurus melas) adjusted buoyancy by altering swimbladder volume becoming less buoyant in current than in still. Extent of adjustment was dependent on size. Tadpole madtom adjusted buoyancy within 96–192 h but partial adjustment occurred within 12–48 h. Year 0 fish made a more rapid decrease in buoyancy than did year 1 or 2. As buoyancy was decreased year 0 and 1 tadpole madtom showed significant changes in internal pressure of swimbladder gases. Black bullhead secreted gases into the swimbladder to increase buoyancy while tadpole madtom showed no such ability.