Science Advisory Report 2019/015

Stock Assessment of Atlantic Cod (Gadus morhua) in NAFO Divisions 4X5Y

Summary

• Catches have remained below the Total Allowable Catch (TAC) of 825 mt in recent years, with landings of 675 mt, 736 mt, and 746 mt, respectively, for years 2015, 2016, and 2017. The Northwest Atlantic Fisheries Organization (NAFO) Divisions 4X5Y Cod commercial fishery catch at age has shown a truncation in age structure since the 1990s. A reappearance of older fish was seen in 2016 and 2017, though their numbers remain low.
• At the 2018 peer review of the assessment framework, a Lower Reference Point (LRP) of 22,193 mt was chosen based on the Sb_50/90 method.
• Considering the stock is currently in the Critical Zone and expected to decline even in the absence of fishing under current productivity conditions, no fishing mortality reference point was proposed at the 2018 framework review.
• Following a variable but generally stable period throughout the 1980s and early 1990s, the population declined throughout the 1990s and 2000s, and has remained at low levels since 2010. The 2018 beginning of year estimate of Spawning Stock Biomass (SSB) from the 3MFfirst Virtual Population Analysis (VPA) model is 10,298 mt, remaining below the LRP of 22,193 mt.
• The levels of recruitment estimated by the 3MFfirst model for this stock have remained below 5 million fish since 2015, with the most recent estimate of the 2016 year class being the lowest on record.
• Fishing Mortality (F) shows a step-wise in all fully recruited ages after 1994, reaching series lows in the most recent time period. The most recent fully recruited F for this stock is estimated at 0.09.
• Under current productivity conditions, there is a high probability that SSB will decrease from 2019 to 2020, even in the absence of fishing.
• The most recent 5-year average of Natural Mortality (M) on Ages 5+ is 1.57, and equates to 21% annual survival. Unless natural mortality is reduced to 0.31, which is 20% of current mortality level and equates to 73% annual survival, there is a very low probability of this stock recovering to the Cautious Zone over the next 10 years.
• Although 4X5Y Cod is regarded as a data-rich stock with age-structured fishery and survey information, periods of bias in the historical catch, changing natural mortality, and stock mixing are problematic for modeling this stock.
• Lack of reliable estimates of unreported catch and discards of Cod from recreational and non-groundfish fisheries in NAFO Divisions 4X5Y restrict the model from accounting for any fishery-induced mortality besides reported catch.
• Many basic ecosystem indicators and the magnitude of their effect on the abundance and distribution of various life stages of Cod are undetermined, hindering the incorporation of ecosystem considerations into the stock assessment.

This Science Advisory Report is from the December 4, 2018, Stock Assessment of Atlantic Cod in NAFO Division 4X5Y. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

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