Sea Technology

JUL 2017

The industry's recognized authority for design, engineering and application of equipment and services in the global ocean community

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www.sea-technology.com July 2017 / st 35 A UVs are part of a rapidly growing fleet of platforms to extend, complement and guide oceanographic obser- vations and ecosystem assessments. Profiling ocean gliders are capable of sampling continuously through the ocean's water column by gliding on wings and adjusting their buoyancy and attitude. Slocum electric ocean gliders by Tele- dyne Webb Research (TWR) are specifi- cally configured to operate in shallow con- tinental shelf environments (less than 200 m). Deployments can last over a month and transit hundreds of kilometers with periodic surfacing to obtain location by GPS, transmit near-real-time oceanographic data, and al- low mission adjustments through the Irid- ium satellite communications system. To record oceanographic physical and chemi- cal parameters for assimilative ocean circu- lation models, other technologies include optical sensors to measure radiance and irradiance, dissolved matter backscatter and chlorophyll, as well as passive acous- tic recorders for animal vocalizations and anthropogenic ocean noise. Government agencies have used ship- based echosounders to assess fish popu- lations and map fish and plankton biomass in the water column over large spatial scales to address ecosystem and fishery management goals. Costs, sea conditions and safety can limit the use of research vessels for fishery assessments, making the development and application of fishery echo- sounders in autonomous platforms an area of targeted re- search. Recent development of small form factor echosounders may provide additional means to collect active acoustic (e.g., fishery sonar) data using ocean gliders to detect bio- mass of marine organisms in the water column in remote locations where limited resources prohibit use of large re- search vessels, or as part of a growing sustained ocean ob- servations network. The glider system can also function in weather and sea conditions that are suboptimal for research vessels. Researchers at NOAA's National Ocean Service, Nation- al Marine Fisheries Service and University of South Florida collaborated with TWR and ASL Environmental Sciences (ASL) to integrate a low-power echosounder into a Slocum electric glider. The goal was to evaluate the functionality of a glider-based simultaneous survey of oceanographic water column variables and continental shelf benthic and pelagic plankton and fish biomass. From Moorings to Moving Platforms ASL has spent more than 20 years developing its multi- frequency Acoustic Zooplankton Fish Profiler (AZFP) in re- Echosounder for Biological Surveys Using Ocean Gliders Extending Fishery Ecosystem Assessments to Remote Places By J. Christopher Taylor • Chad Lembke ASL AZFP echosounder and custom transducer installed in Slocum glider hull section.

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