The effect of missing acoustic observations (dropped pings) onmean area density estimates of Antarctic krill (Euphausia superba)

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Acoustic surveys typically sample continually along transect, and line-transect theory is applied to determine mean area density and variance estimates. However, when the water column under a hull mounted echosounder transducer becomes aerated or the transducer orientation changes rapidly, for example during rough weather, the continuous data are which interrupted as pings are dropped. Current methods ignore missing pings and as a consequence potentially negatively bias acoustic estimates of marine organism density. The purpose of this investigation is to determine if missing pings bias area density estimates of Antarctic krill (Euphausia superba).