The International Pacific Halibut Commission adopted a coastwide stock assessment methodology at its 2008 Annual Meeting. This methodology accommodates movement of halibut at all ages and determines a single coastwide estimate of exploitable biomass. This single coastwide estimate is then apportioned into IPHC regulatory area estimates using data from the fishery-independent IPHC setline stock assessment survey and estimates of bottom area from each regulatory area. This apportionment resulted in a different distribution of the exploitable biomass than had been estimated with the previous closed-area stock assessments.

At the 2008 Annual Meeting, the IPHC Commissioners and industry endorsed the coastwide stock assessment methodology but wished to have further investigation of methods for apportioning the coastwide exploitable biomass estimate into IPHC regulatory area estimates of biomass and catch limits. In addition, the Commission requested that the staff update industry on the most recent results and understanding of halibut movements arising from Commission tagging programs, particularly the PIT-tag experiment. This workshop will address both of these issues. The workshop will be held at the Red Lion hotel in Bellevue, WA on September 4th, 2008. A registration form for the workshop with details on the venue is attached to this News Release. Registration forms must be received by August 15, 2008. An online registration and other workshop information can be found at:
http://www.iphc.washington.edu/halcom/meetings/workshop2008/baw2008.htm.

The workshop will cover: updated information on movement of halibut from PIT and PAT tagging experiments; the survey-based apportionment of coastwide exploitable biomass used by Commission staff for the 2008 catch limit determination; alternate methods to apportion coastwide exploitable biomass; and, estimated impacts on harvest rates and stock biomass from the use of specific apportionment methods. Relevant documents are located on the meeting website at:
http://www.iphc.washington.edu/halcom/meetings/workshop2008/bawdocs.htm

Currently the following documents are available on the above referenced meeting page. Additional documents will be posted here as they become available.

  • IPHC Scientific Report 83 - describes the assessment model and harvest policy as well as describing IPHC tagging programs, the 2008 IPHC stock assessment, biomass apportionment, and yield recommendations
  • Aims of study, external technical review, tagging protocol, holding experiments, and scanning experiments ( IPHC RARA 2002) 
  • Initial work in 2001 on tagging location, holding studies, and a exploration of a state-space approach to analysis (IPHC RARA 2001)
  • Tagging protocol, summary of 2003 shedding studies, recoveries, and preliminary analysis (IPHC RARA 2003) 
  • Simulation of the effect of migration and uneven fishing effort on the selectivity and harvest rate estimates (IPHC Stock Assessment papers - 2004)
  • 2004 releases, tag-loss summary, and summary of 2004 sampling and recoveries (IPHC RARA 2004)
  • A simple recovery model was presented in the paper analyzing the 2004 recoveries (IPHC RARA 2004)
  • A somewhat more complicated model accounting for non-commercial removals of marked fish was presented in the paper analyzing the 2005 recoveries (IPHC Stock Assessment papers - 2004)
  • Analysis of recoveries through 2005 (IPHC RARA 2005)
  • Summary of 2005 sampling and recoveries (pp 253-276), tag loss (pp 279-284), examination of cause for low recoveries (pp 285-292) (IPHC RARA 2005)
  • Analysis of recoveries through 2006 (pp 129-138) and causes of low recoveries (pp 139-144) (IPHC RARA 2006)
  • Summary of 2006 sampling and recoveries (pp 277-298) (IPHC RARA 2006)
  • Fine-scale modeling of migration from tagging data (includes estimation of scanning rates by statistical area) (pp 245-258) and analysis of recoveries through 2007 (pp 259-274) (IPHC RARA 2007)
  • Summary of 2007 sampling and recoveries (pp 399-426) (IPHC RARA 2007)
  • Summary of 2007 assessment, peer review, and migration effects (IPHC RARA 2007)
  • Examination of survey catch rates, fishery-survey interactions, modeling migration, harvest policy (IPHC RARA 2007)
  • Summary of 2008 recommended catch limits (pp 105-110) (IPHC Bluebook 2008)

The workshop will be chaired by an independent scientist. A report of the workshop will be produced for presentation to the Commission in the fall of 2008. Questions on the workshop can be directed to either Laura Black or the IPHC office at (206) 634-1838.

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Bruce M. Leaman
Executive Director
Phone: (206) 634-1838
Fax: (206) 632-2983