Fig. 2. The relationships between breathing parameters as measured by analysis of video recordings or from computerized data acquisition. (A) Correlation between breathing frequencies (f_R) determined by the two methods based on analysis of six different fish exhibiting a wide range of f_R (r²=0.999, y=0.986x+0.687). (B) Correlation between opercular displacement (a measure of breathing amplitude) determined by the two methods during normocapnia and hypercapnia (Pw_CO2=3.5 mmHg). Each plot represents a change in amplitude of a single fish and each fish is represented by a different symbol (N=6). (C) Changes in ventilation amplitude during filming were analogous regardless of the method of measurement; data plotted are taken from B (r²=0.968, y=0.819x+0.119); N=6.