Science Advisory Report 2009/008

Stock assessment of subdivision 3Ps cod

Summary

• Information available to evaluate stock status consisted of commercial landings (1959 to 31 Dec 2008) and log-book data (1997-2008) in conjunction with information from Canadian research vessel (RV) trawl surveys (1972-2008), industry trawl surveys (1997-2005, 2007), and Sentinel surveys (1995-2008). Exploitation (harvest) rates were estimated from tagging experiments.
• Commercial catches by Canada and France combined for the ongoing 2008/09 management year totaled 9,300 t (to 31 Dec 2008), including 25 t from Sentinel surveys. Estimated landings from the recreational fishery in the summer of 2008 were 101 t. The total allowable catch (TAC) for 2008/09 is 13, 000 t.
• Commercial catches by Canada and France combined for the 2007/08 management year totaled 12,875 t, including 28 t from Sentinel surveys. In addition, two independent estimates of landings from the recreational fishery (summer 2007) ranged from 62 t to 217 t. The TAC for 2007/08 was 13, 000 t.
• The assessment concluded from tagging data and ancillary information that the complex of stock components exploited by fisheries in 3Ps does not comprise a single stock for which population biomass and abundance can be estimated from existing information. Therefore the impacts of fishing at specific TAC levels on all stock components could not be quantified.
• However, the DFO RV survey covers most of the stock, and survey trends broadly reflect stock trends.
• Indices from fixed-gear Sentinel surveys conducted shoreward of the DFO RV and industry trawl surveys have been stable in recent years.
• Inshore fish harvesters (<65’ vessel sector) feel that the stability in their catch rates indicates there has been good recruitment and an overall stability in stock status.
• Exploitation rates for most inshore components in 2008 were approximately 10% which seems sustainable.
• The status of inshore components is uncertain, but indicators from the inshore are stable.
• Exploitation rates for offshore cod tagged in the Halibut Channel are not high but have increased in 2005-07.
• Total biomass from DFO RV surveys indicates a decline since 2004. The 2008 biomass estimate is less than 50% of the average for 1997-2008. The survey spawning stock biomass (SSB) is in decline and is near the lowest levels observed.
• Annual total mortality rates (age 5 -11) inferred from the DFO RV survey increased from an average of 23% in 1997-2004 to an average of 55% in 2005-07. This high value is a concern. Although the trend in natural mortality is unknown, fishing mortality has increased.
• Biological indicators of stock health, including growth rates and body condition, do not show any recent trend, but are lower compared to values in the 1980s when the stock was considered more productive and supported fisheries in excess of 30,000 t.
• Recent year-classes supporting the fishery are relatively weak in comparison to the strong 1997 and 1998 cohorts. Although preliminary indications are that the 2006 cohort is strong, this cohort will not recruit to the fishery until 2011.
• The 1997 and 1998 cohorts have now largely passed through the fishery. The 2006 year-class appears strong, and fisheries in 2009 and 2010 should be managed in ways to protect this year-class from premature capture until it has reached a size where it fully contributes to the mature population.
• Offshore harvesters (>65' vessels) see evidence that the relative abundance of the older fish in the offshore component is less than in recent years, and also see evidence of the reasonably strong 2006 year-class. Catch rates in the offshore fishery remain high in traditional areas, but a reduction in the 2009 catch is warranted to risk manage the SSB decline until the 2006 year- class recruits to the fishery.
• The basis for a limit reference point for this stock is B_Recovery, defined as the lowest observed SSB from which there has been a sustained recovery. The 1994 value of SSB has been identified as the limit reference level for this stock.
• Survey SSB has been decreasing in recent years and in 2008 was just above the limit reference point. If management is to be consistent with the Precautionary Approach, catches should be reduced compared to recent levels, and greater priority should be given to increasing SSB.
• If the management goal is to stop the current decline in offshore biomass then a reduction in TAC to 10,000 t is considered the minimum necessary, notwithstanding the uncertainties about survivorship and absolute size of biomass. If the management objective is to ensure growth in offshore biomass, then a greater reduction is considered necessary.
• The 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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