A General Guide for Deriving Abundance Estimates from Hydroacoustic Data










Known Issues

Echosounder calibration programs

Simrad provides the Lobe software program to measure echosounder beam patterns.  Due to concerns about circularity in the beam width measurement process, marine and freshwater groups are divided on how or whether to apply the beam width results.  However, the target strength gain given by the Lobe program is valid.  This gain can be checked by an on-axis calibration. As a result, no consistent approach has been adopted, and discussions among users and the manufacturer continue.  Biosonics does not provide a similar program. 

Environmental effects

Variability in system parameters due to environmental conditions, primarily temperature, has been observed in the EK500.  The temperature effect appears to influence the 120 and 200 kHz transducers more than lower frequencies, and is observed even when absorption and sound speed are properly established.  This effect is believed to be a transducer design issue.  We have no data on this for Biosonics transducers.

Transducer warm-up

Echosounders require a warm-up period before use in a survey or calibration exercise.  A minimum warm-up time of 5 minutes is recommended.