Evaluation of the North-East Arctic saithe (Pollachius virens) acoustic survey
Working paper
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http://hdl.handle.net/11250/105787Utgivelsesdato
1997Metadata
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Since 1985 an acoustic survey specially designed for saithe has annually been conducted in
October-November by the Institute of Marine Research (IMR) on the Norwegian near coastal
banks. Since 1992 the survey has covered the area from the Varangerfjord close to the Russian
border and southwards to 62°N. Because of the schooling behaviour of the saithe, the survey has
tried to cover known saithe grounds rather than sailing regular survey tracks. This paper
describes and tries to make a critical evaluation of this research survey with regards to survey
design, timing, cruise tracks, stratification, fishing ground selection, and attribution of species
composition to acoustic data. Including the acoustic survey in the XSA-tuning will slightly
improve the statistical diagnosis of the assessment, and will lead to a small reduction in fishing
mortality and a 3-10% larger juvenile biomass the four most recent years. For the prediction,
however, the consequences are bigger. The input fishing pattem to the prediction and the stock
size in numbers will lead to 10-12% larger total biomass, up to 40% higher SSB and up to more
than 80% larger catches in the short term when the survey is included in the XSA-tuning. Out of
presently three XSA tuning series, the acoustic survey is the only fishery independent one, it both
improves the reliability and has a significant impact on the results. It is therefore concluded that
the survey should continue to be conducted annually at more or less the same time of the year.