The plainfin midshipman's soundscape at two sites around Vancouver Island, British Columbia

Abstract

The soundscape is an integral habitat component for acoustically sensitive animals. In marine environments, noise pollution from anthropogenic activities is pervasive, potentially leading to negative consequences for marine animals. To understand the impacts of noise pollution, one must first understand the soundscape in which these animals live. Using autonomous passive acoustic recorders, we examined the soundscape of plainfin midshipman fish Porichthys notatus at 2 breeding sites around Vancouver Island, Canada. Plainfin midshipman humming was recorded every night for the 4 wk long recording period; it was a main driver of sound pressure levels, adding more than 6 and 17 dB on average (SE ± 0.8) at each site in the 80 Hz octave band. The fundamental frequency of the hum was temperature-dependent and varied between 76 and 111 Hz. At one site (Ladysmith Inlet), sound pressure level was consistently higher than at the other site (Brentwood Bay), and these differences appeared to be related to anthropogenic noise rather than to plainfin midshipman humming. Although most of the anthropogenic noise occurred during the day and fish humming occurred mostly at night, both anthropogenic noise and midshipman humming occasionally occurred at the same time, suggesting that noise pollution has the potential to impact this species. This study constitutes the first long-term in situ description of the soundscape for the plainfin midshipman. Our results will increase our understanding of teleost soundscapes, a currently critically understudied research area, and shed light on how anthropogenic noise pollution might affect fishes and coastal ecosystems.