Broadband acoustics on the VENUS observatory in Saanich Inlet.

Abstract

High‐frequency sonar is by far the most cost‐effective way of “profiling” the water column from an ocean observing system. From a biological oceanographic perspective, long‐term acoustic observations are rich with information on the depths and abundances of fish and zooplankton. The drawback is that it is difficult to conclusively identify which species (or even functional groups) are present at any given time. This can be done, but only with plenty of supporting data, generally acquired non‐autonomously. Broadband acoustics may be the key to making acoustic observations of fish and zooplankton less qualitative. Here we explore this idea. We present nearly two years (Apr. 2008–Feb. 2010) of broadband (85–155 kHz) echosounder data collected on the VENUS observatory in Saanich Inlet. Using historical and contemporaneous (July 30, 2009) zooplankton net‐tow data, we attempt to automate and interpret the resulting classification of scattering layers throughout the long‐term record.