The echogram below shows schools of mackerel. These are observed using frequencies 18, 38, 70, 120, 200 kHz on a Simrad EK60 scientific echo sounder.
The schools of mackerel can be seen in the left part of the echogram. It is clear that the echo from the schools becomes stronger with increase in frequency. This response is unique to mackerel and can be used to discriminate mackerel from other fish species.
Copyright Kongsberg Maritime AS 2007