Research Document - 2010/102
Assessing the status of the cod (Gadus morhua) stock in NAFO Subdivision 3Ps in 2009 – results from a Zonal Assessment Process (February/March 2009) and a Regional Assessment Process (September/ October 2009)
By B.P. Healey, E.F. Murphy, J. Brattey, N.G. Cadigan, M.J. Morgan, D. Maddock Parsons, D. Power, K. Dwyer, and J. C. Mahé
Abstract
The status of the cod stock in Subdiv. 3Ps was assessed during two separate meetings held in 2009. A zonal assessment process (ZAP) to review the status of five Atlantic Cod stocks including cod in Subdiv. 3Ps was held during February/March of 2009. A regional assessment process (RAP) was held during September/October of 2009, in which stock status was updated based upon information collected and analyzed during the spring and summer of 2009. Principal sources of information available for the assessments were: reported landings from commercial fisheries, oceanographic data, a time series of abundance and biomass indices from Canadian winter/spring research vessel bottom‑trawl surveys, inshore sentinel surveys, science logbooks from vessels < 35ft, industry logbooks for larger (> 35 ft) vessels, and tagging studies. The total allowable catch (TAC) for the 2008/09 fishing season was set at 13,000 t. The TAC was lower for the 2009/10 season, set as 11,500 t. Commercial landings for the 2008/2009 fishery totaled 12,600 t. The 2009/10 fishery was still in progress at the time of the RAP with provisional landings totals of 3,100 t. The removals through recreational fishing is unknown for both 2008 and 2009, but is thought to be a small (~1%) fraction of the commercial landings.
A complex of stock components are exploited in Subdiv. 3Ps. Thus the impact of fishing at specific TAC levels on all components cannot be quantified. However, the DFO RV survey covers most of the stock, and it is thought that survey trends broadly reflect overall stock trends.
Zonal Assessment Process, February/March 2009:
Total biomass from the 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 (as inferred from tagging exploitation rates) has increased. Indices from fixed-gear Sentinel surveys conducted shoreward of the DFO RV and industry trawl surveys have been stable in recent years. 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. Cohort modeling of the survey data indicates that survey SSB has been decreasing in recent years and in 2008 was just above the limit reference point (BRecovery). 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 an even greater reduction is considered necessary.
Regional Assessment Process, September/October 2009:
Cohort analysis of the DFO RV survey data indicated that SSB has declined by 13% per year over 2004-09. It is too early to assess the effect on SSB of the recent reduction in TAC to 11 500 t for the 2009/10 management year. However if the management goal is to ensure growth in SSB, then a further reduction in TAC would increase the probability of growth.
Overall, the findings of the current assessment are consistent with those of previous assessments. However, the current status and recent trends in the stock are somewhat more uncertain due to the nature of the change in the survey index between 2008 and 2009. Several consecutive year-classes (1999-2005) have been relatively weak and are supporting the majority of total landings. This has lead to increased exploitation rates in the offshore, and contributed to an overall reduction in stock size. The 2006 year-class is again estimated to be strong. The probability that the SSB in 2009 is below the LRP varies from 20% to 40% depending on assumptions regarding the catchability of different age fish by the survey.
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