Assessing vessel slowdown as an option for reducing acoustic masking for Arctic cod in the western Canadian Arctic

Noise from this shipping traffic can lead to acoustic masking, reducing the ability of marine animals to detect and use biologically important sounds. Vessel-slow down may be an alternative mitigation option in regions where re-routing shipping corridors to avoid important habitat for fish and marine mammals is not possible. We investigated the potential relief in masking from a 10 knot speed reduction of container and cruise ships. Based on ambient sound measurements and real shipping data, the percentage reduction in the available listening space for fish as a container or cruise ship passes under varying speeds and ambient sound conditions was shown. The mitigation effects from slower vessels (travelling at 15 knots compared to 25 knots), in terms of auditory masking, was equal between ambient sound conditions, but not equal between the type of vessel. Slowing vessels led to a substantial decrease in the listening space reductions, with the amount of reduction varying by distance away from vessels. Vessel slowdown through sensitive habitat could be an effective mitigation strategy for reducing the extent of auditory masking.