Comparing hydroacoustics measurements in large estuaries at two frequencies (70 and 120 kHz)

Acoustic technology in use for over 40 years has proven to be an effective tool to collect high-quality data describing animal size, abundance, behavior (1) across a wide range of spatio-temporal scales in aquatic ecosystems (2). It is considered as compatible with best practices defined by European Directives and applied as an alternative and/or complementary to intrusive net sampling. With the miniaturization of equipment, different echosounders, and frequencies can be used simultaneously on small boats. However, unique features of estuaries have limited the application of hydroacoustics.