Acoustic estimates of saithe in the North Sea in 1984 and 1985
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http://hdl.handle.net/11250/104024Utgivelsesdato
1985Metadata
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This paper describes the results from a joint cruise in July 1984 with
two vessels, and the results from two cruises in February - March
1985.
In July the saithe were standing well above the bottom, but the saithe
were often mixed with high densities of plankton which might result
in too high integrator values for saithe. It is also a problem that
big specimens are more difficult to catch than small ones. This may
result in an overestimation of small fish. The estimate for July were
645 000 tonnes compared with a VPA estimate of 637 000 tonnes.
In February - March the saithe were standing very close to the bottom,
especially at the spawning grounds. The acoustic estimates therefore
give only about 35% of the VPA estimate. The relative abundance of the
year-classes are in good agreement in all estimates. The 1981 and 1982
year-classes seem to be good ones.