Science Advisory Report  2012/078

Stock Assessment of NAFO Subdivision 3Ps Cod

Summary

• Information available to evaluate stock status consisted of total commercial landings from all countries (1959 to 2011), log-book data (1997-2011) in conjunction with information from Canadian research vessel (RV) trawl surveys (1972-2012), an acoustic survey conducted in May 2012, sentinel surveys (1995-2012), and a telephone survey of Canadian fish harvesters pertaining to the 2011/12 fishery. Exploitation (harvest) rates were estimated from tagging experiments in Placentia Bay. Consistent with recent assessments, a survey based cohort model (SURBA) was used to infer overall stock trends.
• Recent reported landings have been less than the TAC, and the proportion of the TAC taken has been decreasing. In the 2009/10 season, 78% of the TAC was landed. At the end of the 2011/12 season, just over half (52%) of the 11,500 t TAC was taken.
• Tagging data and ancillary information indicated that there is a complex of stock components in 3Ps. However, the DFO RV survey covers most of the stock, and survey trends broadly reflect stock trends.
• Sentinel gillnet catch rates have been very low since 1999, and the 2011 gillnet index was the lowest in the time-series. Sentinel linetrawl catch rates from the past three years have also been below average. Gillnet catch rates from logbooks of vessels <35' have been stable since 1999. Linetrawl catch-rates decreased over 2006-10, but increased in 2011 and are presently at the time-series average.
• Average annual exploitation rates based on various size groups of cod tagged and released in Placentia Bay ranged from 17-31% in 2010 but declined to 9-11% in 2011.
• Estimates of total mortality rate from a cohort model (ages 5-10) over 2007-11 plateaued at 0.67.  Total mortality rates reflect mortality due to all causes, including fishing. When the age-specific mortality estimates are weighted by the population number at age, total mortality has been decreasing in recent years, with an average value of 0.50 (40% annual mortality). This mortality is relatively high considering that only half of the 2011/12 TAC was taken.
• Recent recruitment (2004-2009 cohorts) has improved. In particular, the 2006 cohort is estimated to be more than twice the time-series (1983-2012) average. This cohort is expected to be fully recruited to the 2012 fishery.
• The basis for a limit reference point (LRP) 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.
• Over 2009-2012, SSB has increased considerably. The SSB was estimated to be below the LRP during 2008 and 2009. The 2012 estimate is 64% above the LRP, and the probability of being below the LRP in 2012 is very low (0.01).
• Three-year projections were conducted assuming future mortality rates were within ±20% of current values (2009-11 average). Results indicated that SSB will increase if total mortality is reduced, and remain relatively stable if mortality remains at current levels. SSB is projected to decrease if total mortality is above current values. Overall, the probability of being below the LRP in 2013 is very low (0.01 to 0.05). By the end of the projection period (2015) the probability of being below the LRP ranges from 0 to 0.16.

This Science Advisory Report is from the Fisheries and Oceans Canada, Canadian Science Advisory Secretariat, regional advisory meeting of October 9-11, 2012 on the Atlantic Cod in Subdivision 3Ps. Additional publications from this process will be posted as they become available on the DFO Science Advisory Schedule.

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