| Summary: | <p><strong>\"Development of a Multi-Beam Sonar as a Fisheries Tool for Stock Assessment and Essential Fish Habitat Identification of Groundfish in the Western Gulf of Maine\"</strong></p> <p>This data set:<br /> Mean and standard error (S.E.) for numerical abundance, catch-per-unit-effort (CPUE, fish per 30-minute tow), and percent composition (%) of fish enumerated in 10 tows of a 6.5-inch mesh otter trawl by F/V Stormy Weather in Area Closure 133 on 21, 22, and 25 June 2008.</p> <p><u>Abstract</u><br /> Stock assessments based on accurate abundance and distribution data are essential to developing effective management strategies for the Gulf of Maine stock of Atlantic cod, <em>Gadus morhua</em>. The purpose of this study was to prove the concept of using multi-beam sonar as a fisheries tool for studying the behavior and quantifying the abundance of groundfish. The focus of this research was was to develop multi-beam sonar (MBS) as a fisheries survey tool. MBS can complement traditional narrow-beam echosounder and trawl surveys because MBS has a large sampling volume, three-dimensional spatial description, and potentially fewer behavior-related sampling biases than traditional trawl surveys. Relationships between acoustic backscatter and fish biology need to be understood before reliable acoustic surveys using MBS can provide sciencebased information for stock assessments. A series of acoustic and optical measurements were made using 38- and 120-kHz EK60 split-beam echosounders and a 300 kHz EM3002 MBS. These were fixed to a surface platform over a 98 cubic meter submersible cage of 5-cm stretched mesh twine. After standard sphere calibration, the cage was stocked with 195 live Atlantic cod with a mean total length of 80.7 ± 0.8 cm (± standard error; range 51.5-105.0 cm) from nearby spawning grounds 10-15 km off the New Hampshire coast, USA. The sonars were synchronized to collect acoustic data on a captive population of mature cod of known size and number under video surveillance by two underwater cameras. Cod were incrementally removed from the cage to provide a time-series of acoustic backscatter at four densities (n=195, 116, 66, and 23). Preliminary results demonstrate the feasibility of the EM3002 MBS to detect cod and show that quantification of the acoustic backscatter is possible.</p> <p>See <a href=\"http://northeastconsortium.org/ProjectFileDownload.pm?report_id=865&table=project_report\">final report</a></p>
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