Abstract

Hydroacoustic sampling tools are used to survey underwater species’ distributional patterns, abundance, provide bioenergetics modeling validation data, and to assess behavior. Shrimp, fish, and zooplankton species have been monitored using both echo sounding and acoustic telemetry tagging techniques within a broad range of aquatic environments, from large spatial scale studies in open systems evaluating responses to environmental variations to studies in small closed systems monitoring fine spatial scale species-specific interactions. The same basic principles of underwater sound propaga-tion apply to both echo sounding and acoustic telemetry monitoring techniques, providing sampling advantages, but some limitations. Advantages of hydroacoustic biological sampling methodologies include the ability to measure the distribution of organisms over large spatial and temporal scales without disturbing the animals, a high sampling intensity and non-selectivity. Biological assessments employing echo sounders have a limited ability to differentiate species and to resolve targets located close to boundaries such as the surface, bottom or close to underwater structure. These limitations present particular challenges for hydroacoustic evaluations designed to evaluate demersal distributions of shrimp, particularly in regions where fish may also be present. However, resolution of shrimp distributions near the bottom and the ability to segregate shrimp densities from co-located fish aggregations using echo sounders can be optimized via the use of appropri-ate sampling equipment, parameters and analysis approaches.

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