An intership sonar calibration experiment in the Norwegian Sea
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http://hdl.handle.net/11250/105528Utgivelsesdato
1996Metadata
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When migrating in the Norwegian Sea in spring and summertime, the Norwegian spring
spawning herring will be surveyed by vessels from four nations. Because the herring may occur
in schools close to the surface, use of horizontal guided sonar may be an advantage for mapping
the geographic distribution and estimation of abundance. To be able to compare the sonar
recordings of schools obtained by different sonar systems on different vessels, an intership sonar
calibration is nesessary. Such an experiment, which was 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 with an intership distance 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 different 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 implication of the results for cooperative sonar surveys are
discussed.