Beluga Vocalizations Decrease in Response to Vessel Traffic in the Mackenzie River Estuary

Abstract

Vessel traffic negatively affects marine mammals by causing behavioural disturbance, acoustic masking, contamination (i.e., oil spills), and ship strikes. Few studies have examined the effects of vessels on marine mammals in the Arctic, but beluga whales appear to be especially sensitive to vessel traffic. We examine how the vocalizations of belugas are impacted by vessel traffic in the Tarium Niryutait Marine Protected Area in the Mackenzie River estuary of the western Canadian Arctic. Between one and four acoustic recorders were deployed between June and August each year between 2015 and 2018 near the only shipping channel at this site. We examined beluga vocalizations from acoustic recordings over four summers and assessed how the distance to the nearest vessel passing the acoustic recorder affected the number of vocalizations. Beluga vocalizations within the range of the acoustic recorder decreased significantly when vessels were within 5 km of the acoustic recorder. This result suggests either that belugas are avoiding the vessel or that they reduce their vocalization in response to vessel traffic. Future work is needed to assess exactly how belugas are reacting to vessel traffic in this area and what the long-term consequences of these reactions are. Management measures for reducing these impacts must be carefully considered, especially since these vessels are very restricted in where they can travel, and many of the vessels are necessary for the livelihoods of local communities.

The summer soundscape of a shallow-water estuary used by beluga whales in the western Canadian Arctic

“…Any boats that we detected were likely very close to the recorders, given that we only detected most boats for very short periods of time, and the signal almost always included the closest point of approach. We confirmed this point in a recent analysis where we found that vessel tracks derived from Automatic Identification System data did not correlate well with boat noise detected at these recorders (Halliday et al 2019).…”

“…In addition, although belugas evolved around naturally varying ambient sound levels driven by wind and waves, boat noise is a much more recent addition to the soundscape that belugas may have difficulty adequately adapting to. Indeed, belugas have been shown to react to the presence of boats and boat noise at this site (Halliday et al 2019) and at other sites in the Arctic (LGL 1986;Finley et al 1990), often by leaving the area where the noisy activity is occurring (LGL 1986;Finley et al 1990). At this site, specifically, belugas have been shown to react to boats, and likely leave the area when boats are around (Halliday et al 2019).…”

“…Indeed, belugas have been shown to react to the presence of boats and boat noise at this site (Halliday et al 2019) and at other sites in the Arctic (LGL 1986;Finley et al 1990), often by leaving the area where the noisy activity is occurring (LGL 1986;Finley et al 1990). At this site, specifically, belugas have been shown to react to boats, and likely leave the area when boats are around (Halliday et al 2019). However, this reaction was not correlated with detection of boat noise at the acoustic recorder because the shallow water limits the propagation of boat noise; belugas may have been reacting to boat noise that they could hear, but that we were unable to detect.…”

“…At shallow sites such as those used in this study, the shape of the local bathymetry is going to be one of the most important environmental predictors of detection range, simply because low frequency sounds will not propagate through the shallowest water. In a previous analysis, we estimated that beluga vocalizations might be detectable above low ambient sound conditions out to 2 km (Halliday et al 2019). This detection range was confirmed by another recent study in the same system that paired visual observations of belugas with acoustic detections and found that belugas as far away as 2 km were detected acoustically ).…”

“…An additional useful indicator would be to track boats using Automatic Identification System data. We examined this data set in a previous study that also used this same acoustic data set (Halliday et al 2019), and found that boat traffic over the four years of data collection remained relatively stable at these recording sites, with between three and nine Automatic Identification System vessels coming within 10 km of a recording site each year during the recording period. However, Automatic Identification System data should continue to be monitored to track ship traffic in this system.…”