December 7, 2005

International Pacific Halibut Commission Staff Preliminary Catch Limit Recommendations: 2006

Assessment of the status and available yield from stocks of Pacific halibut is conducted annually during the fall and considers the results of research surveys, commercial fisheries and biological studies conducted by Commission staff.  The staff then makes recommendations to the Commission and the halibut industry, for consideration at the Commission’s annual meeting in January.  In making catch limit recommendations for 2006, the staff has considered the results of the analytic assessment, changes in the commercial and survey indices used to monitor the stock, recruitment of incoming year classes, and an updated analysis of an appropriate harvest strategy.  Although the Commission did not adopt the Conditional Constant Catch (CCC) harvest policy recommended by the staff, we retain the framework of threshold and limit reference points together with the mechanism to reduce harvest rate if the threshold reference point is reached.  Changes in the stock biomass as indicated by our catch-at-age assessment as well as some declines in relative abundance indices from our surveys and the commercial fishery were the primary factors influencing our recommendations for 2006.

Catch per unit effort (CPUE) in the 2005 commercial fishery was lower on a coastwide basis, with the exceptions of Area 4A, which was stable, and Area 4B, which saw a modest increase.  Area 4D showed a particularly sharp decline in commercial CPUE, dropping almost 29% from the 2004 value.  Area 3B continued the decline from the peak values of the late 1990s.   

The IPHC setline survey CPUE values showed no consistent trends across the regulatory areas.  Areas 2A, 2C, and 3A survey CPUE values were relatively stable from the previous year.  Areas 2B, 3B, 4A and 4D all showed notable declines in survey CPUE, particularly Area 4D, which dropped by 47%.  After declining almost continuously since the inception of surveys in 1997, the survey CPUE in Area 4B rebounded (18%) from the historic low seen in 2004. 

There were only minor technical changes in the stock assessment analytic model for 2005.  The recruitment of the 1994 and 1995 year classes continues to appear relatively strong in most areas, particularly in Area 3B, although Area 4B is showing a notably low level of recruitment in comparison with other regulatory areas. 

Estimates of exploitation rate, hence exploitable biomass, derived from mark-recapture analysis of PIT-tagged halibut are not used directly for determining recommended catch limits.  The exploitation rates estimated from the analysis of PIT tag returns are similar to those estimated with the catch-at-age analysis in Area 2C, less than the model estimates in Areas 2B and 3A, and are inconsistent with catch rate indices and assessment results for Areas 3B and 4.  Area 2B tag recovery rates by size group suggest a lower rate of capture in 2005 than in 2004 for fish larger than 100 cm.  The lack of tag returns in Area 4 is the issue of greatest concern to the staff.  We do not yet have an explanation for the lack of returns in this area but analytic assessments for Areas 4A and 4B indicate continued declines in exploitable biomass and we choose to rely on these estimates as the most appropriate basis for catch limit recommendations.   

For 2006 we have continued the use of a harvest rate of 22.5% as the baseline harvest rate for the central Gulf of Alaska and southward regulatory areas.  For the western Gulf of Alaska (Area 3B) and Area 4A, we are maintaining a 20% exploitation rate due to concern about the long term productivity of these areas.  For Area 4B, the continued decline in biomass, to the estimated historical minimum, the lack of recruitment, and a new analysis of productivity, has prompted the staff to adopt a lower harvest rate of 15%.  Similarly for Area 4CDE, the sharp decline in survey and commercial catch rates has resulted in the adoption of the 15% harvest rate for this area as well.

Catch Limit Recommendations

The staff recommendations totaling 69.86 million pounds for 2006 are presented in Table 1.  The Area 2A recommendation includes all removals (commercial, treaty Indian, sport) allocated by the Pacific Fishery Management Council's Catch Sharing Plan.  The Area 2B catch limit recommendation includes totals for both the commercial and sport fisheries.  The Canadian Department of Fisheries and Oceans will allocate the adopted catch limit between the sport and commercial fisheries.

The use of a 22.5% harvest rate for Areas 2A-3A in combination with the 2005 estimated constant exploitation yield (CEY) estimate from the stock assessment results in lower recommended catch limits than in 2005 for all regulatory areas except Area 2A.  The catch limit recommendations for 2006 are only slightly lower than 2005 catch limits for Areas 2B, 2C, and 3A.  The recommended decrease in Area 3B is significant and reflects the continuing trend of lower abundance in this area.  The medium-term biomass projections for this area indicate that this trend will reverse within the next several years, as incoming year classes that are estimated to be above average are expected to begin contributing to stock biomass. 

The staff continues to be concerned and exercise caution for the western Gulf of Alaska and the Bering Sea regulatory areas.  Accordingly, a 20% harvest rate is used for regulatory Areas 3B and 4A, and a 15% harvest rate for Areas 4B and 4CDE.  Area 4CDE is treated as a single regulatory unit by the Commission, although the North Pacific Fishery Management Council’s Catch Sharing Plan partitions the Commission catch limit into limits for the individual regulatory areas.  The recommended catch limit for Area 4CDE is lower than the estimated fishery CEY for this area because commercial fishery and survey CPUE values have declined dramatically within this area, raising strong concerns about stock condition.  In addition, the procedure for establishing a catch limit recommendation for the area is influenced substantially by the estimated biomass in Area 4A.  Accordingly, we believe that caution should be used in assigning catch limits to this area and recommend the use of a lower harvest rate for the catch limit calculation.  Staff is continuing its efforts to develop alternate procedures to determine appropriate yield for Area 4CDE. 

The staff continues to recommend a slow rate of increase in catch limits when biomass is increasing and a more rapid reduction of catch limits when biomass is decreasing.  For Area 2A, the staff recommends an increase over the 2005 catch limit equivalent to one-third of the difference between the 2005 catch limit and the estimated 2006 fishery CEY.  For Areas 2B through 4B the staff recommends catch limits that are lower by one-half of the difference between 2005 catch limits and the estimated fishery CEYs for 2006. 

These recommendations, along with public and industry views on them, will be considered by IPHC Commissioners and their advisors at the IPHC Annual Meeting in Bellevue, WA USA, during January 17-20, 2006.  These recommendations are preliminary and, as final data are included in the assessment, may be updated for the Annual Meeting but are not expected to change significantly.

^a Includes sport, tribal, and commercial fisheries
^b Includes sport and commercial fisheries
^c Individual catch limits for Areas 4C, 4D, and 4E are determined by the North Pacific Fishery Management Council catch sharing plan