Variation in glider-detected North Atlantic right, blue, and fin whale calls in proximity to high-traffic shipping lanes

Abstract

Passive acoustic monitoring has become an integral tool for determining the presence, distribution, and behavior of vocally active cetacean species. Acoustically equipped underwater gliders are becoming a routine monitoring platform, because they can cover large spatial scales during a single deployment and have the capability to relay data to shore in near real-time. Yet, more research is needed to determine what information can be derived from glider-recorded cetacean detections. Here, a Slocum glider that monitored continuously for low frequency (<1 kHz) baleen whale vocalizations was deployed across the Honguedo Strait and the associated traffic separation scheme in the Gulf of St. Lawrence, Canada, during September and October 2019. We conducted a manual analysis of the archived audio to examine spatial and temporal variation in acoustic detection rates of North Atlantic right whales (NARWs), blue whales, and fin whales. Call detections of blue and fin whales demonstrated that both species were acoustically active throughout the deployment. Environmental association models suggested their preferential use of foraging areas along the southern slopes of the Laurentian Channel. Results also indicate that elevated background noise levels in the shipping lanes from vessel traffic only minimally influenced the likelihood of detecting blue whale acoustic presence, while they did not affect fin whale detectability. NARWs were definitively detected on less than 20% of deployment days, so only qualitative assessments of their presence were described. Nevertheless, detections of all 3 species highlight that their movements throughout this seasonally important region overlap with a high volume of vessel traffic, increasing their risk of ship strike.