Specialized Tools for Biological Assessment Using Split Beam Hydroacoustics

Hydroacoustics for the assessment of fisheries resources is well established and split beam echosounders are the standard instrument of scientific fisheries acoustics, a technique that utilizing the physics of sound traveling through water to quantify the distribution of biota in the water column. By sending a piulse of sound through the water column and recording the time of travel and the strength of the reflected signal, it is possible to determine the size and location of fish and estimate biomass from the acoustic backscatter.  The science of fisheries acoustics and its applicability to resource management have evolved over the past several decades. Logistical challenges and economic factors continue to drive innovation in the field of hydroacoustics including the integration of split beam echosounders with other systems including UUVs, imaging sensors, and seafloor observatory platforms.  This document provides a description of three recent inventions that facilitate the use of split beam echosounders in non-conventional applications; a hybrid split beam and imaging sonar system tested for defense related applications, an autonomous, submersible echosounder for long-term seafloor observation, and a towed echosounder specifically engineered for use with a self-propelled, autonomous surface vehicle.