Hearing ability of the lined seahorse (Hippocampus erectus).

Abstract

The lined seahorse (Hippocampus erectus), a member of the family Syngnathidae (pipefishes and seahorses), occurs in coastal waters of the western Atlantic, Gulf of Mexico, and Caribbean Sea. This harmless species is listed as “vulnerable” on the International Union for the Conservation of Nature (IUCN) List of Threatened Species, meaning that it has a high risk of extinction in the medium‐term future primarily due to declines in population from targeted catch, bycatch, and degradation of habitat. However, because little is known about hearing in Syngnathids, it is difficult to assess potential effects of anthropogenic sound on these animals. In this study auditory evoked potentials (AEPs) were measured in four H. erectus specimens to determine hearing thresholds and bandwidth. Thresholds were determined using the staircase method with exposures to tone bursts between 50 Hz and 21.6 kHz. At low frequencies H. erectus had AEP thresholds similar to other bony fishes; however, at frequencies above 2 kHz its auditory sensitivity was similar to that of clupeiform species which detect ultrasound [Mann et al., J. Acoust. Soc. Am. (2001)]. The results of this study provide hearing data that can be used to understand potential effects of human‐generated noise on Hippocampus erectus and other seahorse species.