Year‐round changes of ambient noise in freshwater habitats and temperature effects on hearing in fishes

Abstract

Fish get crucial information for their survival from their acoustic environment. Therefore, changes in ambient noise as well as temperature over the year potentially impose great challenges for fishes, especially in freshwater habitats in temperate climates. Noise levels vary more in stagnant habitats such as lakes, backwaters, and streams than in large rivers. The spectral profiles change in stagnant habitats due to biotic noise sources in summer (e.g., stridulating insects), whereas in small streams spectral composition differs due to small changes in water volume, e.g., after snow melt. To investigate possible seasonal effects on fishes, we studied the hearing capabilities of a hearing specialist (Common carp) and a hearing nonspecialist (European perch) at two different temperatures (12 °C and 22 °C) using the AEP recording technique. In the carp the hearing sensitivity decreased up to 12 dB (mean decrease: 4 dB) at 12 °C, whereas no such change was observed in the perch. Latencies of auditory evoked potentials became longer by approximately 0.8 ms at lower temperatures in the carp. The results indicate that auditory sensitivity in hearing specialists is affected by changes in temperature as well as ambient noise throughout the year. [Work supported by FWF.]