Applying an alternative method of echo-integration

Estimators of mean Echo Value Constant (the ratio between echo abundance and the number of fish) in an alternative echo-integrating method were tried with the SIMRAD EK 60 split-beam echosounder. The mean fish-density estimates of NE Arctic cod were compared with corresponding estimates by the classical echo-integration method; the two methods gave similar results. The alternative method uses integrated single-fish echoes, and a new algorithm to extract and integrate single-target echoes is introduced and used. This algorithm uses echo shape and angle stability, not echo amplitude, to test for the presence of single-target echoes. Apparent single-target echoes with a dynamic range of 60 dB in integrated echo intensity were extracted.