International Council for the Exploration of the Sea
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Report of the Northern Pelagic and Blue Whiting Fisheries Working Group (WGNPBW)

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posted on 2023-03-14, 10:18 authored by ICESICES

The ICES northern pelagic and blue whiting fisheries working group (WGNPBW) met for 7 days in August 2006 to assess the state of two stocks, blue whiting and Norwegian spring spawning herring. Age-based assessments were carried out for both stocks.  This year an update of the Icelandic capelin was also made, but last year it was assessed in NWWG.
For blue whithing 5 assessment models were used to explore the data  All models show the same trend in spawning stock biomass and fishing mortality.  Historically they are at similar levels, but depart from each other in recent years.  Final assessment was made with SMS. The spawning stock biomass in 2006 is estimated at 5 million tons.  The assessments indicate a decline in spawning stock biomass from 2005 to 2006, which is not seen in the spawning stock surveys.  Recruitment has been exceptionally good since 1996, but indices from surveys suggest that year class 2005 is a poor one.
During the working group meeting an evaluation of the "Arrangement for the Multi-Annual management of the Blue whiting Stock" was made.  Simulations done by the working group indicated that limiting interannual changes to 100 thous. tons as in the agreement would lead to increased fishing mortality in coming years when the goal was to reduce the fishing mortality gradually from current level to 0.32.  See conclusions in 4.13.4.  
Three models were used to explore the data of Norwegian spring spawning herring. Contradictory to earlier years they all gave the same perception of the current stock size. Final assessment was done by the same model as last year.  This year's assessment is an upward revision of last year's assessment.  There are many reasoning for this. This year tagging data could not be used as the tagging effort is not enough and magnets to detect tags are only located in Norway. The last 4 years in the winter survey are excluded, as it is believed that they have not covered the whole stock.  The 2002 year class is estimated strong and is considered now almost fully matured, which is exceptional at age 4. The spawning stock biomass is estimated at almost 11 million tons and has not been larger since 1957, but it is dominated by 4 years old herring, that is the 2002 year class.
Regarding the development of a new joint Russian-Norwegian assessment model for Norwegian spring spawning herring then it has changed to be a joint model framework. It is aimed to have a working prototype at WGNPBW in 2007.  
Since 2001 the Icelandic capelin have changed their migrations and distribution so radically that with the present state of knowledge it has proven impossible to predict the abundance of the adult stock in the manner used successfully for numerous years previously.
The working group nominates Frans van Beek and Morten Vinther as the next co-chairs for the group. 


Published under the auspices of the following ICES Steering Group or Committee

  • ACFM

Published under the auspices of the following ICES Expert Group or Strategic Initiative



ICES Expert Group Reports

Meeting details

24-30 August 2006; Copenhagen

Recommended citation

ICES. 2006. Report of the Northern Pelagic and Blue Whiting Fisheries Working Group (WGNPBW), 24-30 August 2006, ICES Headquarters. ICES CM 2006/ACFM:34. 294 pp.

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