Harbour porpoises react to low levels of high frequency vessel noise

Abstract

Cetaceans rely critically on sound for navigation, foraging and communication and are therefore potentially affected by increasing noise levels from human activities at sea. Shipping is the main contributor of anthropogenic noise underwater, but studies of shipping noise effects have primarily considered baleen whales due to their good hearing at low frequencies, where ships produce most noise power. Conversely, the possible effects of vessel noise on small toothed whales have been largely ignored due to their poor low-frequency hearing. Prompted by recent findings of energy at medium- to high-frequencies in vessel noise, we conducted an exposure study where the behaviour of four porpoises (Phocoena phocoena) in a net-pen was logged while they were exposed to 133 vessel passages. Using a multivariate generalised linear mixed-effects model, we show that low levels of high frequency components in vessel noise elicit strong, stereotyped behavioural responses in porpoises. Such low levels will routinely be experienced by porpoises in the wild at ranges of more than 1000 meters from vessels, suggesting that vessel noise is a, so far, largely overlooked, but substantial source of disturbance in shallow water areas with high densities of both porpoises and vessels.

Effect of construction-related activities and vessel traffic on marine mammals

“…Both short-term (Thompson et al 2013a) and long-term displacement (Teilmann & Carstensen 2012) as well as changes in foraging behaviour (Pirotta et al 2014) have been reported as likely consequences of construction-related activity to this species. In addition, harbour porpoises are also likely to actively avoid vessels (Hermannsen et al 2014, Dyndo et al 2015; however, despite the present study finding evidence of constructionrelated activity reducing porpoise occurrence in the bay, it did not find any such pattern with respect to the number of vessels within the bay. Conversely, an increase in vessel numbers did have a strong, negative influence on the occurrence of common dolphins.…”

A sense of scale: Foraging cetaceans' use of scale‐dependent multimodal sensory systems

“…Dolphins living in human‐dominated coastal environments may be detrimentally effected by acoustic masking of important informational signals at these micro to fine scales (particularly if vessel noise is within the species’ hearing range; Dyndo et al . , Veirs et al . ).…”

Bubble curtains attenuate noise from offshore wind farm construction and reduce temporary habitat loss for harbour porpoises

“…4 & 6; clearly at the 14−16 km range and likely also at the 8 km range). This reduction above 1 kHz is particularly interesting with respect to impact on harbour porpoises, as thresholds for negative phonotaxis are strongly frequency dependent ) and a strong correlation between reactions in captive porpoises to passing ships and frequency content above 1 kHz has been demonstrated (Dyndo et al 2015). If the energy above 1 kHz is also more important than the low frequencies for pile-driving noise, it becomes important to account for the spectral content of the noise in the assessment and regulation of the impact of pile driving.…”