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Research Document - 2008/086

Assessments of the cod (Gadus morhua) stock in NAFO Divisions 2J3KL (April 2007 and April 2008)

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 in 2007 and again in 2008. A directed “stewardship” fishery and a recreational fishery for cod were re-opened in the inshore during 2006 and continued in 2007; the offshore remained closed to directed fishing in both years. There was no formal TAC, but commercial fishers were permitted an allowance of 3,000 lb of cod per license holder in 2006 and 2,500 lb in 2007. Recreational fishers were permitted 5 fish per day or 15 fish per boat. Reported landings in 2006 were 2,679 t, including 380 t in the recreational fishery, 159 t in the sentinel surveys, and 45 t of by-catch. Reported landings in 2007 (excluding the recreational fishery) were 2,546 t, comprising 2,192 t of directed catch, 172 t of by-catch mainly in the turbot gillnet test fishery, and 182 t in the sentinel surveys. Two widely differing estimates of recreational catch were available for 2007, but the differences could not be reconciled. Commercial fishers also reported that commercial landings are underestimated; hence total catch for the 2007 fishery is uncertain. Offshore and inshore components of the northern cod stock complex have shown different dynamics since the mid‑1990’s and the status of cod in the offshore and three inshore regions (northern, central and southern) were evaluated separately at each assessment.

2007 assessment: Offshore abundance and biomass indices in 2006 were the highest observed since the early 1990’s, but the average index values during 2004-06 compared to the average of the 1980’s were 4-5% (for abundance) and 3-4% (for biomass). Total mortality of cod in the offshore is extremely high (average 58% per year) and recruitment has been weak since 1989. The high rate of mortality is a major impediment to stock recovery and it is recommended that the moratorium on directed fishing be continued, and that by-catch be minimized. For the inshore northern area, it is inferred from the low catch rates in the sentinel surveys (1995-2004) and the commercial fishery (1998-2002) that cod densities have been very low. However, sentinel catch rates increased during 2005 and again in 2006. The origins of the fish generating these increases remain uncertain. They appear to be immigrants, possibly from the offshore; therefore, it would be prudent to keep catches low in this area. A sequential population analysis (SPA) for the inshore central area indicated that spawning stock biomass (SSB) is ~20,000 t and has been increasing since 2003, but exploitable biomass (age 4+) decreased by 6% from 2006 to 2007. Incoming recruitment is estimated to be substantially weaker, which will result in a decline in exploitable biomass and SSB. Projections indicated that the risk of the SSB growing by less than 5% by 1 January 2008 increases rapidly with a catch above 500 t and is very high (0.87) for a catch of 2,500 t. The risk of the SSB growing by less than 5% per year by 1 January 2010 is very high (0.93) even with no catch. For the inshore southern area (southern 3L), the fisheries during 1998-2002 and 2006 were partly dependent on fish that migrate seasonally between 3Ps and 3L. Since the magnitude of annual migration cannot be predicted, the effect of various levels of removals cannot be estimated.

2008 assessment: Offshore abundance and biomass indices increased further in 2007 and show an increasing trend since 2003, most noticeably in southern 3K and northern 3L. The average index values during 2005-07 compared to the average of the 1980’s were 7-8% (for abundance) and 4-5% (for biomass). A notable finding was a substantial decline in total mortality and the prospects for stock recovery have improved. Specific limit reference points for this stock have not been established, but the stock remains well below any reasonable limit reference point and recruitment remains weak; it is therefore recommended that the moratorium on directed fishing in the offshore be continued.  For the inshore northern area in 2007, commercial catch rates improved but sentinel catch rates were largely unchanged and remain lower than those in the inshore central area; therefore, it is recommended that removals in this area be minimized. The SPA for the inshore central area could not be continued in 2008 because the total catch for the 2007 fishery was uncertain. Sentinel fishery catch rates for the inshore central area improved in 2007, are currently above average, and have been increasing since 2002; stewardship fishery catch rates also improved in 2007 and are higher than in earlier fisheries during 1998-2002. These results suggest that exploitable biomass in the inshore central area has increased recently, but this trend may not continue as incoming 2003-06 year-classes are weak. The impacts of fishing at specific catch levels could not be quantified in the absence of a population model. For the inshore southern area (southern 3L), sentinel gillnet catch rates have been unchanged since 2003 but are below average; stewardship fishery catch rates improved but are lower than those in the central area. The fishery in this area continues to be influenced by migrants from 3Ps; the extent of annual migration cannot be predicted, therefore, the effect of various levels of removals from this area cannot be estimated.

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