Correction: Lagrois et al. Low-to-Mid-Frequency Monopole Source Levels of Underwater Noise from Small Recreational Vessels in the St. Lawrence Estuary Beluga Critical Habitat. Sensors 2023, 23, 1674.

There was an error in the original publication [...].

Low-to-Mid-Frequency Monopole Source Levels of Underwater Noise from Small Recreational Vessels in the St. Lawrence Estuary Beluga Critical Habitat.

Anthropogenic noise from navigation is a major contributor to the disturbance of the acoustic soundscape in underwater environments containing noise-sensitive life forms. While previous studies mostly developed protocols for the empirical determination of noise source levels associated with the world's commercial fleet, this work explores the radiated noise emitted by small recreational vessels that thrive in many coastal waters, such as in the St. Lawrence Estuary beluga population's summer habitat. Hydrophone-based measurements in the Saguenay River (QC, Canada) were carried out during the summers of 2021 and 2022. Shore-based observations identified 45 isolated transits of small, motorized vessels and were able to track their displacement during their passage near the hydrophone. Received noise levels at the hydrophone typically fell below the hearing audiogram of the endangered St. Lawrence Estuary beluga. Monopole source levels at low frequencies (0.1-≲2 kHz) held on average twice the acoustic power compared to their mid-frequency (≳2-30 kHz) counterparts. The speed over ground of recreational vessel showed a positive correlation with the back-propagated monopole source levels. Estimations of the mid-frequency noise levels based on low-frequency measurements should be used moderately.

Avoiding sharp accelerations can mitigate the impacts of a Ferry's radiated noise on the St. Lawrence whales.

Exposure to anthropogenic noise from the commercial fleet is one of the primary constituents of the acoustic pollution perturbing the environment of aquatic life. Merchant ships (e.g. bulkers, tankers) have been the focus of numerous studies for underwater noise source level determination and modeling. This work extends pre-existing studies to the ferry ship class. Hydrophone-based measurements of the N.M. Trans-Saint-Laurent ferry near the Rivière-du-Loup harbor (Rivière-du-Loup, QC CANADA) were obtained for 186 transits between 2020 July 22th and 2020 September 5th. For each transit, monopole source levels are estimated for two (2) different modes of operation i.e., the low-speed phases of acceleration/deceleration when the ferry launches/docks at Rivière-du-Loup and the passages at quasi-operational speed at the hydrophone's closest-point-of-approach. Relative differences between the two (2) modes of operation are presented here in the low-frequency domain between 141 and 707 Hz. An average excess of 8 to 11.5 dB indicates that the ferry is likely one order of magnitude noisier, within this frequency band, during acceleration/deceleration when compared to passages at operational speed. This highlights that, in terms of marine mammal conservation, a significant reduction of the noise pollution could be achieved, for instance, by avoiding sudden speed changes in the vicinity of whales.

Agent-based modelling reveals a disproportionate exposure of females and calves to a local increase in shipping and associated noise in an endangered beluga population.

Vessel underwater noise (VUN) is one of the main threats to the recovery of the endangered St. Lawrence Estuary Beluga population (SLEB). The 1% yearly population decline indicates that the cumulative threats are already beyond sustainable limits for the SLEB. However, a potential threefold increase in shipping traffic is expected within its critical habitat in the coming years resulting from proposed port-industrial projects in the Saguenay River. Current data indicate that SLEB typically use multiple sectors within their summer range, likely leading to differential VUN exposure among individuals. The degree of displacement and spatial mixing among habitats are not yet well understood but can be simulated under different assumptions about movement patterns at the individual and population levels. Here, we propose using an agent-based model (ABM) to explore the biases introduced when estimating exposure to stressors such as VUN, where individual-centric movement patterns and habitat use are derived from different spatial behaviour assumptions. Simulations of the ABM revealed that alternative behavioural assumptions for individual belugas can significantly alter the estimation of instantaneous and cumulative exposure of SLEB to VUN. Our simulations also predicted that with the projected traffic increase in the Saguenay River, the characteristics making it a quiet zone for SLEB within its critical habitat would be nullified. Whereas spending more time in the Saguenay than in the Estuary allows belugas to be exposed to less noise under the current traffic regime, this relationship is reversed under the increased traffic scenario. Considering the importance of the Saguenay for SLEB females and calves, our results support the need to understand its role as a possible acoustic refuge for this endangered population. This underlines the need to understand and describe individual and collective beluga behaviours using the best available data to conduct a thorough acoustic impact assessment concerning future increased traffic.