Volume scattering and acoustic single targets detected from VAMPIRE: A Lagrangian profiling vehicle with down- and horizontal-looking transducers

Le résumé fourni par la source

The mesopelagic environment is understudied relative to its size and ecological importance due to sampling challenges. Observations of key variables like mesopelagic animal abundance and biomass have high uncertainty in large part due to the unknown acoustic scattering properties (target strength, TS) of mesopelagic organisms which are difficult to measure using conventional sampling strategies. To help close this data gap, we have developed VAMPIRE, a 0–1000 m rated Lagrangian profiling vehicle equipped with a broadband split-beam echosounder (38, 70, and 200 kHz transducers), optical cameras, and environmental sensors. The acoustic transducers are actuated and can be oriented downward or horizontal to measure animal scattering properties and tracks from orthogonal sampling perspectives within a single survey. We present the first results from this acoustic sampling strategy from deployments in the Sargasso Sea and the Gulf of California from 0 to 600 m depth. We find significant TS distribution differences at specific depth bands between the horizontal and down-looking sampling perspectives useful to infer aspects of animal behavior, such as preferred depth ranges, orientation, and movement patterns within the measured environment. This work expands knowledge of the depth-dependent acoustic scattering properties of mesopelagic animals which are needed for accurate interpretation of acoustic measurements.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.