Passive acoustic monitoring power analysis: a tool for designing an acoustic monitoring program

Monitoring trends of marine mammal populations are notoriously challenging, as density and abundance estimates are frequently characterized by high levels of uncertainty. Statistical power is described as correctly detecting a trend when one is present and is influenced by the uncertainty surrounding the input parameters. The “AVADECAF” tool evaluates the power of a fixed Passive Acoustic Monitoring (PAM) array to detect changes in animal density, via simulation. The simulations can be based on existing surveys or can be used to design monitoring programs. The tool allows for density estimation via distance sampling where ranging of acoustic detections is possible, or Spatial Capture Recapture (SCR), when an animal’s sounds can be detected on more than one of the acoustic sensors. The tool provides an opportunity to evaluate how the power to detect population declines might be improved by comparing alternate survey designs. Improving statistical power increases the probability of detecting a change in the population and can reduce the required duration of a monitoring program. The AVADECAF tool was applied to simulated Blainville’s beaked whale clicks detected by hydrophones at the US Navy’s Atlantic Undersea Test and Evaluation Center (AUTEC), and the potential future applications of this tool are discussed.