A cinematographic investigation into the fish's bioelectric breathing signal

The buccal‐ventilatory movements of bluegill sunfish, Lepomis macrochirus and fathead minnows Pimephales promelas and strip chart recordings of these movements were filmed simultaneously. The amplitudes of the ventilatory signals were greatest when a fish was perpendicular to the plane of either electrode, and the polarity of a signal corresponded to the fish's direction to one of the electrodes. The most common breathing waveforms for both species reflected a bimodal pattern. These patterns varied in frequency and shifted toward single modality in response to stress. Portions of the recorded waveforms consistently coincided with the period in which a fish was displaying either full opercular flare or closure. Similar occurrences corresponded with mouth positions. Several commonly occurring variations of the ventilatory signal waveforms are presented, including the response of bluegill sunfish to a strong concentration of chlorinated water.