Science Advisory Report  2015/061

Assessment of Atlantic cod (Gadus morhua) in the southern Gulf of St. Lawrence (NAFO Div. 4T-4Vn (Nov. – April)) to 2014

Summary

• The cod-directed fishery has been closed since 2009, with a 300 t TAC in place to cover by-catch in other groundfish fisheries, a limited recreational fishery, scientific purposes, and negotiated Aboriginal food, social and ceremonial agreements.
• Annual landings since 2009 have varied between 103 and 172 t.
• Since 2009, the exploitation rate has averaged 0.2% for ages 5-8 and 0.7% for ages 9+. These low levels have a negligible impact on the population trajectory.
• The biomass index for commercial-sized cod (≥ 42 cm) from the annual DFO research vessel survey was at the lowest level observed in the 44-year record in 2011 and 2012. The 2011 and 2012 indices were about 10% of the already low values in 1995-2002. The 2013 and 2014 indices were marginally higher, about 20% of the 1995-2002 level.
• The biomass index from the sentinel trawl survey was at the lowest level observed in 2012 and 2013, averaging 17% of the level at the start of this time series in 2003. The index in 2014 increased to 34% of the 2003 value, but was highly uncertain.
• The biomass index from the sentinel longline program steadily declined from 2004 to 2011. The 2011 value was 19% of the 1995-2004 average. The index remained low in 2012-2014.
• Over the past 15 years, cod have progressively moved out of shallow inshore waters and into deeper offshore waters during their feeding season in the sGSL. This appears to result from the high and increasing risk of predation by grey seals in inshore waters in summer.
• Estimated spawning stock biomass (SSB) declined steadily between 1997 and 2014.  SSB at the beginning of 2014 was 28,700 t, 28.7% of the level in 2000 and 9% of the level in 1985. SSB in 2015 was slightly higher at 34,000 t, 29.2% of the level in 2000.
• A limit reference point (LRP), the level below which the stock is considered to have suffered serious harm to its productivity, was estimated in 2003 to be 80,000 t. The SSB in 2015 is estimated to be 42% of the LRP. There is no chance that the stock is at or above the LRP.
• Year-class strength has been declining since the mid-1980s due to declining SSB. Year-classes produced since 2002 have been the weakest on record, except for the 2011 year-class. The 2011 year-class is estimated to be nearly twice the average size of other year-classes produced since 2002.
• Extremely high natural mortality of cod 5 years and older is the reason for the lack of recovery of this stock. Natural mortality of about 18% annually (M= 0.2) is considered normal for adult cod. In this population, natural mortality of adults has increased over the past 35 years and is now estimated to be 52 - 58% annually (M = 0.74 – 0.88). Predation by grey seals is considered to be a major component of this mortality.
• Given the relatively strong 2011 year-class, SSB is expected to increase slightly in 2016. It is then expected to decline below the 2015 level by 2020 due to the high level of natural mortality.
• At the current level of natural mortality, recovery of this stock is highly improbable, even in the absence of fishing.

This Science Advisory Report is from the March 12, 2015 meeting on Assessment of Atlantic Cod (Gadus morhua) of the southern Gulf of St. Lawrence (NAFO Div. 4T-4Vn (Nov. – April)). 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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