As the use of hydroacoustic devices in fish ecology and fisheries is steadily increasing, a gapless knowledge is needed for assuring the correctness of results from echosounding analysis. To close this gap a bit further, a study was carried out to determine whether two different approaches of echo integration yield similar results if applied to the same dataset. The main difference between the two sub-methods (SED-based and track-based) is that the SED-based approach takes the target strength

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... S) of each single echo detection (SED) into account seperately, whereas the track-based approach summarizes more than one SED to form a fish track from which the mean TS is calculated. We compared data from three lakes, collected at both day- and nighttime, as well as in different seasons. No significant differences in the results of the two echo integration methods could be found. Both approaches yielded similar fish abundance and biomass results. Length classes of fish in the lakes did not differ between methods, but between day and night. The time of the data collection (time of the year, day or night) had a major impact on both abundance and biomass results. Therefore we conclude that the methods are stable in their outcomes, but the comparability of hydroacoustic surveys is strongly affected by vertical as well as horizontal fish distribution in the course of the day and the year.