Exploratory measurements using a broadband, split beam echo sounder system.

A prototype broadband echo sounder has been used for measuring zooplankton and fish in a new collaborative project between the Institute of Marine Research and Kongsberg Maritime‐Simrad. The prototype system used is a Simrad broadband system which includes a transceiver operating from 10–500 kHz. We have mainly used the transceiver together with four separate Simrad ESXX‐7CD standard pressure resistant transducers, the ES70‐7CD, ES120‐7CD, ES200‐7CD, and ES333‐7CD, covering the band from 50 to 450 kHz. The research has so far concentrated on data output formats, calibration methods, and measurements from single targets in ex situ and in situ situations. Examples of recorded reflected spectra for selected calibration and biological targets will be shown and the potential for improved aquatic ecosystem assessment discussed.