Research Document - 2006/088

2006 Assessment of Pollock in 4VWX and 5Zc

By Stone, H., P. Perley, and D. Clark

Abstract

Fishery removals from the Western pollock stock component (4Xopqrs+5Yb+5Zc) averaged 6000 t since 2000 and contributed 92% of total landings in 2005. Mobile gear catch rates in 2006 were at the second lowest level in the time series. Catch rates for 2005 and 2006 were not comparable to those observed earlier in the time series when quotas were not limiting. The 2006 RV biomass index was at the highest observed level in the time series, and although this was an obvious year effect, there has been a general increasing trend since 2003. Other surveys indicated a general trend of increasing rather than decreasing abundance for pollock and supported recent trends from the DFO RV survey. Fishery weights at age, which are used as a proxy for population age 5+ weights at age, have been decreasing since about 1984. RV survey weights at age for these age groups did not show this same declining trend, indicating that the fishery weights may be influenced by changes in fishing patterns. Using a Modified Base VPA (which excludes 2005 and 2006 from the catch rate index), age 4+ biomass has increased from a low of about 7500 t in 2000 to 30000 t in 2006. The 2001 year class is estimated at nearly 15 million recruits and is the strongest since the 1980 year class. Reduced quotas and harvests have contributed to a decline in fishing mortality rates on ages 6-9, which is now just below the F_ref of 0.2. The range of harvest strategies in the 2007/2008 fishing year that are risk averse (25% risk of exceeding F_ref) to risk neutral (50% risk of exceeding F_ref) are about 4400 t to 5300 t.

Landings from the Eastern Component (4Xmn+4VW) traditionally come from the Tonnage Class (TC) 4+ sector, and have been following a declining trend. Since 1993, much of the Eastern Component was closed to cod-directed fishing, which further reduced pollock landings from that area. Research vessel (RV) summer survey biomass, while variable, has been declining since the late 1980s and is now at the third lowest level in the time series. Large scale directed pollock fisheries should not be considered until the Eastern Component rebuilds.

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