In making catch limit recommendations for 2009, staff has considered the results of the analytic assessment, changes in the commercial and survey indices used to monitor the stock, estimated recruitment of incoming year classes, and a harvest policy that reflects coastwide policy goals. The staff also drew on the outcome of both the September 2008 Biomass Apportionment Workshop and recent regional meetings with industry. Detailed results of these additional investigations will be reported in the 2008 Report of Assessment and Research Activities. Ongoing tag returns from the coastwide PIT tagging program continue to demonstrate that regulatory areas cannot be treated as closed management units. Changes in the stock biomass as indicated by our analytic assessment as well as changes in relative abundance indices from our surveys and the commercial fishery were also influential in our recommendations for 2009.
With the exceptions of Areas 2C, 4A, and 4D commercial catch per unit effort (CPUE) in 2008 decreased from 2007 values. The 2008 IPHC setline survey CPUE values increased in Areas 2B, 4A, 4B, and 4D but decreased in all other areas. These fluctuations were generally in the 10% range.
The analysis of optimum harvest rates for the coastwide assessment conducted in 2006 resulted in a target harvest rate of 20% of coastwide exploitable biomass. The staff examined multiple alternatives, including industry suggestions, for apportioning the estimated coastwide exploitable biomass among regulatory areas and concluded that the use of the IPHC setline survey data offered the most standardized and consistent data with which to achieve this partitioning. However, the staff also recognized some regional differences in hook competition with other species and applied an adjustment to accommodate that feature. Accordingly, the distribution of biomass, as determined by the three-year average CPUE of legal-sized fish obtained on the stock assessment survey adjusted for hook competition, was used to partition the coastwide exploitable biomass estimate into regulatory area biomass totals. The staff also removed an adjustment that was applied in Area 2A for the 2008 apportionment following reanalysis of the depth distribution of survey data compared with bottom depth distribution. While the 20% harvest rate is appropriate for the majority of the stock, a harvest rate of 15% is indicated by the analysis of productivity for Areas 4B and 4CDE conducted in 2005, and a similar analysis for Area 4A conducted in 2008. Therefore, staff recommended Catch Limits for Area 4 use a 15% harvest rate. Fishery statistics and biological characteristics of halibut in Area 3B are also of some concern to staff and a detailed analysis of this area will be conducted in 2009.
Catch Limit Recommendations for 2009
The staff recommendations totaling 54.01 million pounds for 2009 are presented in the following table. The Area 2A recommendation includes all removals (commercial, treaty Tribes, and sport) allocated by the Pacific Fishery Management Council's Catch Sharing Plan. 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 Area 2B catch limit recommendation includes totals for 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 catch limit recommendations are made with the assumption that both Canada and the U.S. will manage to their domestic targets for sport fish catch.
The use of a coastwide assessment and apportionment of coastwide biomass based on survey estimates of distribution creates some substantial changes in Total Constant Exploitation Yield (Total CEY) and recommended catch limits among areas, compared to previous assessments. Lower recommended catch limits are identified for Areas 2, 3A, 4A, and 4CDE while Areas 3B and 4B have somewhat higher recommended catch limits. These differences are associated with the different distribution of biomass associated with survey apportionment of a coastwide total biomass, compared with the previous biomass distribution estimated from closed-area assessments, as well as CPUE changes in both the survey and the commercial fishery. As noted in the 2007 stock assessment, the distribution of biomass based on survey estimates is more consistent with other estimates of biomass distribution that are independent of the stock assessment.
The staff continues to recommend a slow rate of increase in catch limits when estimated CEY is increasing and a more rapid reduction of catch limits when CEY is decreasing (a Slow Up - Fast Down policy). For Areas 2, 3A, 4A, and 4CDE the staff recommends catch limits that are lower by one-half of the difference between 2008 catch limits and the estimated fishery CEYs for 2009. For Areas 3B, and 4B, the staff recommends an increase over the 2008 catch limit equivalent to one-third of the difference between the 2008 catch limit and the estimated 2009 fishery CEY.
The staff recognizes that adoption of the coastwide assessment and survey apportionment results in a significant shift in the estimated distribution of exploitable biomass. This analysis concludes that exploitation rates on the eastern portion of the stock have been too high in the past decade, resulting in lower biomass in Area 2 than would be realized if harvest rates had been near the target level. In the longer term, a lowered harvest rate will permit rebuilding of the exploitable biomass in Area 2 and an increase in available yield. The pace of that rebuilding will be affected by the strength of year classes recruiting to the fishery over the next several years.
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 Vancouver, BC Canada, during January 13-16, 2009. 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.
Proposals concerning changes to catch limits should be submitted to the Commission by December 31, 2008. Catch limit proposals are available on the Commission's web page (http://www.iphc.washington.edu/halcom/default.htm) or from the Commission's office. Additional details about the Annual Meeting can also be found on the web page.
Table 1. IPHC staff recommended catch limits for 2009, by IPHC regulatory area (million lbs, net weight). The 2008 fishery catch limits are included for comparison.
|Regulatory Area||2008 Fishery Catch Limit||2009 IPHC Staff Recommended Fishery Catch Limit|
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.
Figure 1. International Pacific Halibut Commission Regulatory Areas