Vessel noise cuts down communication space for vocalizing fish and marine mammals

Abstract

Anthropogenic noise across the world's oceans threatens the ability of vocalizing marine species to communicate. Some species vocalize at key life stages or whilst foraging, and disruption to the acoustic habitat at these times could lead to adverse consequences at the population level. To investigate the risk of these impacts, we investigated the effect of vessel noise on the communication space of the Bryde's whale Balaenoptera edeni, an endangered species which vocalizes at low frequencies, and bigeye Pempheris adspersa, a nocturnal fish species which uses contact calls to maintain group cohesion while foraging. By combining long-term acoustic monitoring data with AIS vessel-tracking data and acoustic propagation modelling, the impact of vessel noise on their communication space was determined. Routine vessel passages cut down communication space by up to 61.5% for bigeyes and 87.4% for Bryde's whales. This influence of vessel noise on communication space exceeded natural variability for between 3.9 and 18.9% of the monitoring period. Additionally, during the closest point of approach of a large commercial vessel, <10 km from the listening station, the communication space of both species was reduced by a maximum of 99% compared to the ambient soundscape. These results suggest that vessel noise reduces communication space beyond the evolutionary context of these species and may have chronic effects on these populations. To combat this risk, we propose the application or extension of ship speed restrictions in ecologically significant areas, since our results indicate a reduction in sound source levels for vessels transiting at lower speeds.

Localizing individual soniferous fish using passive acoustic monitoring

“…However, it was stated by the authors of this study that some of the boatwhistle frequencies would be below the absolute cut-off frequency (~ 1000 Hz) (Fine and Lenhardt, 1983) meaning theoretically acoustic propagation cannot be measured and accurate recordings of sound cannot be taken (Officer, 1958). To accurately investigate an animal's communication space, the acoustic behavior (source level, frequency range and/ or hearing threshold) of the species in question the local sound propagation conditions must be understood (Putland et al, 2017). Propagation of low frequencies in shallow waters is a very complex phenomenon where refraction and reflection will play an important role (Bass and Clark, 2003;Mann, 2006).…”

The Effects of Ship Noise on Marine Mammals—A Review

“…A decrease in communication range as a result of increased levels of ship noise has also been modeled for Bryde's (Balaenoptera edeni), fin (Balaenoptera physalus), humpback, and minke whales (Balaenoptera acutorostrata) Cholewiak et al, 2018;Gabriele et al, 2018;Putland et al, 2018). The Lombard effect comprises changes in the spectral features of vocalizations (i.e., in frequency and level) and in vocalization rates, in order to compensate for masking (Lombard, 1911).…”

Ecology of sound communication in fishes

“…They calculated a considerable decrease in distance in the presence of various anthropogenic noise sources (e.g. Putland et al, 2017;Stanley, Parijs, & Hatch, 2017;Van Oosterom et al, 2016;Vasconcelos et al, 2007). These calculations, however, need to be treated cautiously because none of them provide baseline communication distances or additional evidence that fish maintain constant sound levels.…”

“…Among fishes, the acoustic detection of predators is the least investigated ecological constraint, whereas noise or more precisely noise pollution has become a hot topic (Cox, Brennan, Gerwing, Dudas, & Juanes, ; Popper & Hawkins, ; Putland, Merchant, Farcas, & Radford, ; Radford, Kerridge, & Simpson, ; Slabbekoorn et al., ). Anthropogenic noise is thought to endanger fish populations.…”