Science Advisory Report2009/025

Pollock in div. 4VWX+5

Summary

Western Component

• Since 2000, fishery removals have averaged 6,000 t. The Western Component of the management unit contributed 87% and 81% of total landings in 2006 and 2007.
• Estimates of Age 4+ (considered spawning stock) biomass declined from about 66,000 t in 1984 to about 7,500 t in 2000. Biomass has been rebuilding since 2000, increasing steadily to about 29,000 t in 2007, but declining to 27,000 t in 2008.
• The 2001 year-class is estimated to be the strongest since the 1988 year-class. Early indications for the 2004 and 2005 year-classes are that they are the lowest in the time series.
• Fishing mortality rates steadily increased from the early 1980s to above 1.0 by the early 1990s and remained high until the early 2000s. Subsequent reduced quotas and harvests as well as increasing population biomass have contributed to a decline in the fishing mortality rate on ages 6-9, which has been below the F_ref of 0.2 since 2006.
• The range of harvest strategies in the fishing year that are risk averse (25% risk of exceeding F_ref) to risk neutral (50% risk of exceeding F_ref) is about 3,700 to 4,400 t. If fished at F_ref, the projected 2009/2010 Age 2+ catch biomass is 4,100 t. At this level of harvest, Age 5+ population biomass will decrease from 2009 to 2010.
• If recruitment at Age 2 for the 2004 and 2005 year-classes is not as low as the model estimates and is set to the lowest level in the time series (3.4 million), the range of harvest strategies is about 4,100 to 4,750 t. If fished at F_ref, the projected 2009/2010 Age 2+ catch biomass is 4,500 t, and at this harvest level, population biomass is expected to stay the same from 2009 to 2010.
• These harvest strategies are for 4Xopqrs+5 and would be conservative if applied to all of 4X+5, which is the current approach used by FAM.

Eastern Component

• Landings from the Eastern Component, traditionally from the Tonnage Class (TC) 4+ sector, have declined substantially. Since 1993, much of the Eastern Component has been closed to cod and haddock directed fishing, which further reduced pollock landings from this area.
• DFO research vessel (RV) summer survey biomass, while variable, followed a declining trend from the early 1990s to 2006, the third lowest level in the time series. Since then, the index has increased to levels not seen since the mid-1990s. Most of the recent increase is attributed to higher catches from RV survey tows in 4Xmn and not in 4VW. Directed pollock fisheries in the Eastern Component should proceed with caution.
• DFO RV indices for the Eastern Component show a different pattern from the Western Component, with more Age 3 and Age 4 fish present for the past two years.

Ecosystem Considerations

• The current level of observer coverage in 4X is far too low to provide meaningful bycatch estimates, but spiny dogfish appears to be the most commonly discarded bycatch species, with other species occurring at low levels.
• The habitat over which the directed pollock fishery takes place is highly energetic and of high complexity. The impact of the pollock fishery on the sea floor is currently unknown.
• The diet of pollock from the Scotian Shelf and Bay of Fundy has shown decadal changes, with euphausiids (krill) being the predominant prey in the 1960s and 1980s, less so in the 1990s, but have been predominant again since 2003.

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