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An intership school-counting experiment using sonar in the Norwegian Sea
Misund, O.A.; Jákopsstovu, S.H. (1997). An intership school-counting experiment using sonar in the Norwegian Sea. Sarsia 82: 153-157
In: Sarsia. University of Bergen. Universitetsforlaget: Bergen. ISSN 0036-4827, more
Peer reviewed article  

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  • Misund, O.A.
  • Jákopsstovu, S.H.

    During their spring and summer migrations in the Norwegian Sea, Norwegian spring-spawning herring may be surveyed by vessels from several nations. Because the herring may occur in schools close to the surface, horizontal guided sonar may be useful for mapping their geographic distribution and estimating their abundance. To be able to compare the sonar recordings of schools obtained by different sonar systems on different vessels, an intership school counting experiment is necessary. Such an experiment, which is the first of its kind, was conducted in the Norwegian Sea in June 1995. Vessels from the Faroe Islands, Iceland, Norway and Russia lined up at intership distances of one nautical mile, and headed in the same direction at a speed of about 4 m s -1 over a total distance of 30 nautical miles. The number of schools recorded from 50-300 m to the side of the individual vessels was quite similar, but the correlations between the number of schools recorded by the different vessels declined the smaller the sampling distance unit. The implications of the results for cooperative sonar surveys are discussed.

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