The repeatability of fish biomass and size distribution estimates obtained by hydroacoustic surveys using various sampling strategies and statistical analyses

摘要

Successive hydroacoustic surveys were conducted on a small lake in the Jura Mountains (eastern France) to test several sampling strategies and methods of calculation. The results show that night samples give a better picture of the fish populations than daytime ones; that parallel transect surveys are the ones easiest to conduct, and that, all the survey designs tested, gave statistically equivalent biomass estimations and size distributions. The results obtained are also similar for all the statistical calculation methods used. Repeated samplings on several successive days gave similar results for the estimated biomass and fish size structure in the hypolimnion, but gave different results for the fish populations in the epilimnion. As part of the Water Framework Directive monitoring of fish populations, these hydroacoustic methods can be used to estimate fish stocks, and to track their change over time and spatial differences, but they need to be combined with complementary sampling methods.