Data from: Wall structure and material properties indicate viscous damping of swimbladder sounds in the oyster toadfish Opsanus tau

Despite rapid damping, fish swimbladders have been modeled as underwater resonant bubbles. Recent data suggest that swimbladders of sound-producing fishes utilize a forced rather than a resonant response to produce sound. The reason for this discrepancy has not been formally addressed, and we demonstrate, for the first time, that structure of the swimbladder wall will affect vibratory behavior. Using the oyster toadfish Opsanus tau, we find regional differences in bladder thickness, directionality of collagen layers (anisotropic bladder wall structure), material properties that differ between circular and longitudinal directions (stress, strain and Young’s modulus), high water content (80%) of the bladder wall, and a 300 fold increase in modulus of dried tissue. Therefore the swimbladder wall is a viscoelastic structure that serves to damp vibrations and impart directionality, preventing the expression of resonance.