Potential impact of mid-frequency active sonar on whales from passive acoustic monitoring data

Abstract

Behavioral response studies of tagged whales have documented an adverse reaction to mid-frequency active sonar (MFAS). The relationship between MFAS and the acoustic behavior of whales is complex and requires accounting for natural variability in species presence. We examine the acoustic response of Cuvier’s beaked whales (Ziphius cavirostris) and blue whales (Balaenoptera musculus) from long-term acoustic recordings at three sites in Southern California waters from 2009 to 2015. Presence and absence were marked in 1-min bins for all signal types. Generalized estimating equations (GEEs) were used to model relationships between species acoustic detection and temporal and sonar covariates while accounting for residual temporal autocorrelation. Both species showed considerable temporal variability in calling. Modeling at one site showed decreased detections of beaked whale echolocation clicks when sonar signals had higher received levels at the recorders and when the proportion of bins containing sonar increased. On cessation of sonar signals, beaked whale detection increased over periods of up to about a week. Analyses of blue whale response and a comparison of multiple sites will also be presented. This work represents substantial progress in our understanding of the impact of MFAS on cetaceans, which is crucial for effective context-dependent management of anthropogenic activities.