For example, 1 knot can be written as 1 kn or 1 kt. Knots can be abbreviated as kn, and are also sometimes abbreviated as kt. Confidence intervals and p-values (via Wald-statistics approximation) were calculated with the function sjt.lmer of the sjPlot package 34.One knot is equal to a speed of one nautical mile per hour, or one minute of latitude per hour. The term “mixed” indicates that the model implies the use of at least one fixed effect (i.e., a variable for which we wish to quantify the effect on reported broadband source levels) and at least one random effect (in our case, the time of the day of the measurement). Generalized linear mixed model (GLMM) analysis was conducted with the function lmer of the lme4 package 33. Generalized linear mixed modelĪ multi-parameter maximum likelihood approach via the minimization of the Akaike information criterion was used to assess the dependency between the ferry’s MSLs and its speed with emphasis on transits at CPA where recorded speeds in this work compare with the ferry’s operational speed (see Table 1). Shallow waters play the role of high-pass filters regarding underwater noise propagation with the lowest transmitted frequency \(f_\)] values calculated for episodes of sharp acceleration/deceleration variations at launching/docking in Rivière-du-Loup harbour (Fig. Some SLEB’s high-residency areas within their critical habitat are located in shallow waters with depths around 10 m 22, 23. Moreover, several low-frequency species of baleen whales use the SLE as a feeding ground 20, 21, making them vulnerable to the low-frequency noise emitted by ferries 10. However, the biologically critical contact calls that belugas are known to use for group cohesion and to maintain mother-calf contact contain significant acoustic energy at a broad range of frequencies, including low frequencies 6, 18, 19. Lawrence whales’ soundscape.īeluga whales are considered to be mid- or high-frequency cetaceans 17. With ferries accounting for the largest cumulative number of transits in the SLEB’s critical habitat 14, 15, 16, this segment definitely deserves more attention with regard to impacts on the St. So far, the estimation of MSLs in the SLE has mainly focused on commercial shipping 12 and to a lesser extent on whale-watching excursion vessels 13, with no effort devoted to other segments of the marine traffic. A ship’s MSLs are equivalent to its far-field frequency-dependent radiated noise corrected for surface reflections also known as Lloyd’s Mirror effects 11. One of the fundamental goal identified by this action plan is to assess the monopole source levels (MSLs) of all vessels operating in the SLEB’s critical habitat. This led the federal government to develop the Action Plan to reduce the impact of noise on the SLEB and other marine mammals at risk in the SLE 10. VUN was identified as one of the three most critical threats limiting SLEB recovery. Lawrence Estuary beluga (SLEB) which is protected under the 9. Lawrence Estuary (SLE) and the Saguenay Fjord (Québec, Canada) are impacted by VUN, including the endangered population of the St. Several marine mammal populations that use the St. Impacts of VUN on whales such as belugas include behavioral disruption 3, changes in vocalizations 4, masking 5, 6, and hearing loss 7, 8. Vessel underwater noise (VUN) is known to threaten aquatic life 1 including marine mammals 2. 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. 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. Relative differences between the two (2) modes of operation are presented here in the low-frequency domain between 141 and 707 Hz. 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. 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. Hydrophone-based measurements of the N.M. This work extends pre-existing studies to the ferry ship class. bulkers, tankers) have been the focus of numerous studies for underwater noise source level determination and modeling. Exposure to anthropogenic noise from the commercial fleet is one of the primary constituents of the acoustic pollution perturbing the environment of aquatic life.