December 3, 2003

In making catch limit recommendations for 2004, staff has considered the results of the analytic assessment, changes in the commercial and survey indices used to monitor the stock, the implications of separate male and female assessments, and an appropriate harvest strategy. Consideration of all of these elements and, the latter two in particular, lead us to recommend caution in setting catch limits for 2004.

Commercial catch rates in 2003 improved or were stable with those of 2002 in Areas 2A through 3A, with a notable increase in Area 3A (Fig.1). Those in the western Areas 3B and 4 continued their decline of recent years. In all of these western areas, commercial CPUE has been declining since 2000 and in the case of Areas 4C and 4D, for longer periods. The coherence of CPUE changes in these latter two areas is consistent with the staff’s view that Areas 4C/D/E comprise a single stock management unit. However, with the exception of Area 4C, the commercial CPUE in regulatory sub areas of Area 4 is near the long-term average value.

In contrast, the IPHC setline survey CPUE values decreased in 2003 in all regulatory areas. The declines in Areas 2C and 3A are from higher CPUE values seen in 2002, and are now similar to the CPUE observed in 2001. Western area survey CPUE values continued to show declines similar to the commercial CPUE values.

The major changes in the stock assessment for 2003 are the development of a sex-specific model for the stock with a length-specific selectivity to estimate age-specific selectivity, and the first analytical estimates of abundance for Areas 3B, 4A, and 4B. Previously, the sexes have been combined in the IPHC stock assessment but the change in halibut growth rates over the past decade and the consequent effect on the selectivity of fish by age has prompted the staff to separate the sexes for assessment.

The Conditional Constant Catch (CCC) policy, outlined at the 2003 IPHC Annual Meeting, will be recommended to the Commission for adoption and use in the management of the Pacific halibut stock. The CCC policy uses a ceiling harvest rate and a ceiling (or cap) on total removals as a means to stabilize harvest over longer periods.

The analytic stock assessment has been conducted on a sex-specific basis for the first time. Our recommendations have been developed in consideration of the differences in selectivity of males and females from previous estimates, which have been determined by this work, and the use of an appropriate harvest rate (0.25) for such a change.

The staff recommendations totaling 73.69 million pounds 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. For the first time, the Area 2B catch limit recommendation includes totals for the commercial and sport fisheries. The Department of Fisheries, Canada will allocate the adopted catch limit between the sport and commercial fisheries.

The Area 3A estimated exploitable biomass for 2003 increased considerably over the previous year but we believe some caution is required before this estimate should be adopted. Accordingly, we are recommending that the catch limit for Area 3A be increased by only 50 percent of the potential increase. The stock assessment indicates lower biomass in Area 3B and we recommend using this estimate.

We are concerned that the productivity of the Bering Sea halibut is less than that of the Gulf of Alaska and more southerly areas. Accordingly, we recommend continuation of a 0.20 exploitation rate for this area until either the results of a recent tagging experiment or continued application of the analytic model indicate a higher rate is appropriate.