Estimating uncertainty in whale location following visual or acoustic detection: Implications for dynamic management of North Atlantic right whales


The USA and Canada employ dynamic management strategies to improve conservation outcomes for the endangered North Atlantic right whale. The tactics rely on near real-time knowledge of whale distribution generated from visual surveys and opportunistic sighting reports. Although near real-time passive acoustic monitoring systems have been operational for many years they have, for the most part, not been incorporated in dynamic management due to 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 detection. The goals of this study were to estimate uncertainty in right whale location following acoustic and visual detection, and identify the timescale at which uncertainties in the location of acoustic and visual detections become equal owing to post-detection whale movement. We simulated whale movement using an auto-correlated random walk model parameterized to approximate three common right whale behavioural states (traveling, foraging, and socializing). We then used a Monte Carlo approach to estimate whale location over a 96-hour period given the initial and evolving uncertainties arising from the acoustic and visual detection methods and whale movement. The results demonstrated that for either detection method the uncertainty in whale location increases rapidly following initial detection and can vary by an order of magnitude after 96 hours depending on behavioural state. The uncertainty in whale location became equivalent between visual and acoustic detections within 24 to 48 hours depending on right whale behaviour and acoustic detection-range parameterization. The results imply that using both visual and acoustic detections provide enhanced information for the dynamic management of this visually- and acoustically-cryptic and highly mobile species.

North Atlantic Right Whale Consortium Meeting
Portland, Maine, USA