Estimating North Atlantic right whale (Eubalaena glacialis) location uncertainty following visual or acoustic detection to inform dynamic management

Abstract

The United States and Canada employ dynamic management strategies to improve conservation outcomes for the endangered North Atlantic right whale (Eubalaena glacialis). These strategies rely on near real-time knowledge of whale distribution generated from visual surveys and opportunistic sightings. Near real- time passive acoustic monitoring (PAM) systems have been operational for many years but acoustic detections of right whales have yet to be incorporated in dynamic management because of concerns over uncertainty in the location of acoustically detected whales. This rationale does not consider whale movement or its contribution to location uncertainty following either visual or acoustic detec- tion. The goal of this study was to estimate uncertainties in right whale location following acoustic and visual detection and identify the timescale at which the uncertainties become similar owing to post-detection whale movement. We simu- lated whale movement using an autocorrelated random walk model parameter- ized to approximate three common right whale behavioral states (traveling, feeding, and socializing). We then used a Monte Carlo approach to estimate whale location over a 96-hr period given the initial uncertainty from the acoustic and visual detection methods and the evolving uncertainties arising from whale move- ment. The results demonstrated that for both detection methods the uncertainty in whale location increases rapidly following the initial detection and can vary by an order of magnitude after 96 hr depending on the behavioral state of the whale. The uncertainties in whale location became equivalent between visual and acoustic detections within 24–48 hr depending on whale behavior and acoustic detection range parameterization. These results imply that using both visual and acoustic detections provides enhanced information for the dynamic management of this visually and acoustically cryptic and highly mobile species.

Publication
Conservation Science and Practice
Date
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