Fig. 4. Relationship between number of pulses per sound and total sound duration for courtship–female-visit, nest preparation, aggressive 1–2 pulse and aggressive >2 pulse sounds produced by the Hawaiian sergeant fish, Abudefduf abdominalis. There is a positive linear relationship between pulse number and sound duration for all four sound types. Coefficient of determination (r²), linear regression statistics, sample sizes and line equations for each sound type are as follows: courtship–female-visit (r²=0.84, P<0.001, N=78, y=5.4x+1.3); nest preparation (r²=0.78, P<0.001, N=38, y=3.3x+1.6); aggressive 1–2 pulse (r²=0.22, P=0.02, N=26, y=2.1x+1.2); aggressive >2 pulse (r²=0.62, P<0.001, N=37, y=3.1x+2.4).