Research Document - 2010/103
Assessment of the cod (Gadus morhua) stock in NAFO Divisions 2J+3KL in 2010
By J. Brattey, N.G. Cadigan, K. Dwyer, B. P. Healey, M.J. Morgan, E.F. Murphy, D. Maddock Parsons, and D. Power
Abstract
The status of the northern cod (Gadus morhua) stock in NAFO Div. 2J+3KL was assessed through a Regional Assessment Process (RAP) held in St. John’s, NL during 15-19 March and 22-23 March 2010. A directed commercial cod fishery and a recreational fishery were re-opened in the inshore during 2006 and continued in 2007-2009; the offshore remained closed to directed fishing. There was no formal TAC during 2006-2009, but commercial fishers were permitted an annual allowance (3,750 lb per license holder in 2009). Recreational fishers were permitted 5 fish per person per day, up to a maximum of 15 fish per boat. Total catch in 2009 is uncertain. Reported landings in 2009 were 3,098 t, including 2,832 t in the stewardship fishery, 216 t in the sentinel surveys, and 50 t taken as by-catch, but excluding recreational fishery removals. There are no direct estimates of recreational landings for 2009. However, analysis of tag returns suggests that recreational fishery removals during 2009 could be 64% of reported stewardship fishery removals.
In the absence of reliable catch information the assessment was based mainly on a cohort analysis of the autumn DFO research vessel (RV) trawl survey data and tagging. The cohort analysis provided relative estimates of stock size and absolute estimates of total mortality (Z). For the recent period (2008-2009) estimates of fishing mortality (F) obtained from tagging and acoustic telemetry data were used to partition Z into F and natural mortality (M). Total biomass has increased (23% per year) since 2004. Spawning stock biomass (SSB) increased (83% per year) from 2004 to 2008, but the 2009 value was similar to 2008. Total mortality in the offshore was high (Z=1.0 to 1.5) during 1996-2002, but has subsequently declined in spite of the re-opening of directed fishing in the inshore during 2006-2009. Average annual Z during 2007-2009 (ages 4-8) was 0.42 (=35% mortality per year). Analysis of tagging data indicated that fishing mortality (F) on offshore cod during 2008 and 2009 was 0.06 and 0.02 (=5% and 2% per year), respectively. Similar estimates of F were obtained for cod tagged inshore during 2007-2009 (range 0.02 to 0.10), suggesting that recent fishing mortality has been a small component of total Z. The 2003 and 2004 year-classes are weaker than those produced in 1998-2002 and have now entered the SSB; consequently, the recent rate of stock growth is unlikely to continue in the short term. Subsequent year classes (2005 and 2006) appear average for the 1993-2007 period.
In the inshore, analysis of age-disaggregated sentinel catch rate data indicate that exploitable biomass increased in the central inshore area during 2003-2008, but was lower in 2009 than in 2008 in all inshore areas. The 2003 and 2004 year-classes are notably weaker than those that have supported recent fisheries (2000 and 2002 year classes). Consequently, exploitable biomass is likely to decrease further in 2010 even with no removals. If current levels of removals are maintained then exploitation rates are expected to increase in 2010.
Overall, the status of the stock has improved, particularly during 2004-2008. The average autumn survey SSB index over the last 3 years (2007-2009) is 10% of the average during the 1980’s. However, the improvements are limited to areas adjacent to the 3KL border and the central portion of the inshore. The stock has not increased across much of the historical geographic range. Recruitment has not improved in spite of recent increases in stock size. Although specific limit reference points for this stock have not been established, overall the stock is well below any reasonable limit reference point and remains in the critical zone with respect to the precautionary approach (PA). Application of the PA would require that any catch in 2010 be at the lowest possible level. This would include no directed fishing and measures to reduce cod by-catch in other fisheries. Management should focus on promoting further increases in SSB and improved recruitment until the stock is more resilient to the effects of fishing.
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