Science Advisory Report  2010/019

Stock Assessment of Northern (2J3KL) cod in 2010

Summary

Catch

• Total catch in 2009 is uncertain. Accurate catch information is needed to evaluate the impact of future fishery removals on stock growth.
• Reported landings in 2009 were 3,098 t. This included 2,832 t in the stewardship fishery, 216 t in the sentinel surveys, and 50 t taken as by-catch, but excludes recreational fishery removals.
• There are no direct estimates of recreational landings for 2009. However, analysis of tag returns suggests that removals from recreational fisheries during 2009 could be 64% of the stewardship fishery removals.

Offshore

• Based on a cohort analysis of the autumn DFO research vessel (RV) trawl survey, total biomass has increased (23% per year) since 2004. Spawning stock biomass (SSB) increased (83% per year) from 2004 to 2008, but the 2009 value was similar to 2008.
• Total mortality in the offshore was extremely high during 1996-2003 and was a major impediment to stock recovery. Total mortality has declined substantially since 2003 and this has been an important factor in the recent increase in total biomass and SSB.
• The 2003 and 2004 year-classes are weaker than those produced in 1998-2002 and have now entered the SSB; consequently, the recent rate of stock growth is unlikely to continue in the short term. Subsequent year classes (2005 and 2006) are estimated at about the 1993-2007 average.
• The average survey SSB estimate in the offshore over the last 3 years is 10% of the average during the 1980’s and is concentrated adjacent to the 3K/3L border.
• The number of young fish (ages 2 and 3) in the offshore survey in the 1990s and 2000s has been consistently much lower than during the 1980s. Further stock growth will require an improvement in recruitment which has not been observed to date.
• Offshore tagging and telemetry indicate that a substantial portion of cod from an offshore aggregation migrated to the inshore of 3KL during the summer. Exploitation of these offshore cod in the inshore was low, estimated at 6% in 2008 and 2% in 2009.

Inshore

• Sentinel catch rates suggest that exploitable biomass in 2009 was near the 1995-2009 average, but lower than in 2008 for the northern, central and southern inshore regions.
• In the inshore northern area catch rates are lower than those in the central area suggesting lower exploitable biomass in the northern area. Fisheries in this area depend on seasonal immigration of fish, possibly from offshore regions, including 2J where offshore biomass remains low. Therefore, it is recommended that removals from this area be minimized.
• During 2007-2009, mean exploitation rates from tagging studies were low and ranged from 3-10% among inshore central and southern areas.
• In the inshore central area, catches depend on resident inshore components and seasonal migrants from the offshore.
• Exploitable biomass in the central inshore area is likely to decrease further in 2010 even with no removals. The 2003 and 2004 year-classes are weaker than those produced in 2000 and 2002, and the 2002 year-class is moving out of the exploitable biomass. Therefore, if current levels of removals are maintained then exploitation rates in the central inshore area are expected to increase in 2010.
• In the inshore southern area, catches are partly dependent on seasonal immigration of fish from the offshore of 3KL, and from 3Ps where the stock is declining.
• The 2009 industry telephone survey showed most harvesters in 2J3KL felt that cod were more abundant during 2009 than in the 1980s.

Whole stock

• Although a specific limit reference point has not been established, the stock is clearly below any reasonable value. The application of the precautionary approach would require catches in 2010 to be at the lowest possible level. This would include no directed fishing and measures to reduce cod by-catch in other fisheries.
• Current levels of removals have resulted in low exploitation rates and probably have had little impact on recent stock dynamics. In general, the 2003-2005 year-classes are weaker than those from 1999-2002. Consequently, even with no fishing, the recent (2004-2008) high rate of growth in SSB is unlikely to continue in 2010. Current levels of removals will not greatly affect the rate of change in SSB in 2010.

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