Assessing acoustic communication active space in the Lusitanian toadfish

Abstract

The active space of a signal is an important concept in acoustic communication as it has implications on the function and evolution of acoustic signals. However, it remains mostly unknown for fish since it has been measured in only a restricted number of species. We combined physiological and sound propagation approaches to estimate the communication range of the Lusitanian toadfish's (Halobatrachus didactylus) advertisement sound, the boatwhistle (BW). We recorded BWs at different distances from vocalizing fish in a natural nesting site at circa 2-3 m depth. We measured the representation of these increasingly attenuated BWs in the auditory pathway through the auditory evoked potentials technique (AEP). These measurements point to a communication range ranging between 6 to 13 m, depending on the spectral characteristics of the BW. A similar communication range (circa 8 m) was derived from comparing sound attenuation at selected frequencies with auditory sensitivity. This is one of the few studies that combines auditory measurements with sound propagation to estimate the active space of acoustic signals in fish. We emphasize the need for studies to consider that active space estimates should take informational masking into account.