Acoustic communication plays an important role in the social behaviours of vocal teleost fishes in the Family Batrachoididae (midshipman and toad fishes). The midshipman and toadfishes have become good models for investigating the neural and endocrine mechanisms of auditory perception and vocal production shared by all vertebrates, in part, because the reproductive success of these batrachoidid fishes is highly dependent on acoustic communication. The plainfin midshipman fish (Porichthys notatus), like other teleost fish, use the saccule as the main acoustic end organ for hearing to detect and locate vocalizing mates that produce multiharmonic advertisement calls during the breeding season. Recent work showed that the frequency sensitivity of the peripheral auditory system changed seasonally with female reproductive state such that reproductive females became better suited than non-reproductive females to encode the higher harmonics of the male’s advertisement call. Approximately one month before the breeding season, females showed peaks in circulating plasma levels of testosterone and 17beta-estradiol, which are now known to induce the female’s summer reproductive auditory phenotype and enhance auditory sensitivity to the dominant higher harmonic components of the male’s mate call. Furthermore, midshipman-specific oestrogen receptor alpha and androgen receptor have been identified in the saccule which now provides additional support for a direct steroid effect on the inner ear. Additional physiological evidence will be presented that suggests that the saccular hair cell receptors are the prime candidate sites for this novel form of steroid-dependent auditory plasticity. I will discuss why this auditory plasticity may represent an adaptation to enhance mate detection and localization during the breeding season.