Science Advisory Report  2009/009

Stock Assessment of Northern (2J3KL) cod in 2009

Summary

• Reported total landings from all fisheries in 2008 (stewardship, recreational, Sentinel survey, and by-catch) were 4,162 t. Landings from the stewardship fishery were 3,089 t, which includes 121 t of by-catch in the winter flounder and turbot test fisheries. In addition, 254 t were landed in the Sentinel surveys.
• Landings from the 2008 recreational fishery were estimated at 818 t based on results from a telephone survey. This estimate is likely to be revised when weights based on actual sampling of recreational fishery catches become available. Tag returns also suggest that recreational landings may be higher than the available estimate.
• Based on autumn DFO research vessel (RV) trawl surveys, offshore abundance and biomass indices have been increasing since 2003; spawning stock biomass (SSB) has been increasing since 2005. The average abundance, biomass, and SSB of cod in the offshore over the last 3 years are 8% of the average during the 1980’s.
• Most of the autumn offshore RV survey abundance (50%) and biomass (75%) is concentrated adjacent to the 3K/3L boundary. This region encompasses only 14% of the total surveyed offshore area of 2J3KL, and in the 1980s contained <20% of survey abundance and biomass.
• Total mortality in the offshore was extremely high during 1996-2003 and has been a major impediment to stock recovery. Total mortality has declined substantially since 2003 and the prospects for stock recovery have improved.
• The recent increase in offshore biomass is mostly due to improved survival and the continued growth of the 2002 year-class, and the appearance offshore after 2005 of the 2000-01 year-classes.
• Winter acoustic surveys in 2007 and 2008 found a dense aggregation of cod in a traditional over-wintering area along the shelf edge in southern 3K. The aggregation in 2008 was much larger than was observed in 2007, and included approximately 20% mature fish.
• Offshore tagging and telemetry in 2008 indicated that a substantial portion of cod from the offshore aggregation migrated to the inshore of 3KL during the summer, and some were caught in inshore fisheries. Exploitation of offshore cod in the inshore was estimated at 6%.
• The new evidence of inshore migration indicates that the moratorium in the offshore is no longer sufficient to protect the offshore stock until recovery is well established.
• The 2008 industry telephone survey showed most harvesters in 2J3KL felt that cod were more abundant during 2008 than during 2007.
• Current cod growth rates and condition indicate that some aspects of stock productivity have improved over values in the 1990s and early 2000s; however, age at maturation remains low. These components of productivity are below the levels observed in the 1980s when biomass and harvests were much larger.
• Year-class strength in the offshore in the 1990s and 2000s has been poor compared to the 1980s.
• 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 2009 to be at the lowest possible level. This would include no directed fishing and measures to reduce cod by-catch in other fisheries.
• Although status offshore has improved, the stock has not increased across much of its historical range and overall remains far below historical biomass levels. Management should focus on promoting further increases in SSB and improved recruitment until the stock is more resilient to the effects of fishing.
• Exploitation rates on offshore cod by inshore fisheries have been low enough to permit growth in biomass of some offshore components; exploitation rates should not be allowed to increase.
• For assessment purposes the inshore was divided into three areas: 1) a northern area (2J and northern 3K); 2) a central area (southern 3K and northern 3L); and 3) a southern area (southern 3L).
• During 2008, mean exploitation rates from tagging studies ranged from 3-7% among inshore central and southern areas.
• However, recruitment information suggests that exploitable biomass in inshore areas in 2009-10 is likely to be similar to 2008-09. To achieve the same exploitation rates as in 2008, total removals (recreational plus commercial) should not increase.
• In the inshore southern area, catches are partly dependent on seasonal immigration of fish from 3Ps where the stock is declining. Future removals may therefore rely more heavily on cod from the offshore of 3KL.
• In the inshore northern area, catch rates are lower than those in the central area suggesting lower cod abundance 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 to minimize removals from this area.
• Any fishery should be managed such that catches are not concentrated in ways that result in high exploitation rates on any stock components.

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