Science Advisory Report 2008/034

Stock Assessment of Northern (2J3KL) cod in 2008

Summary

• Reported total landings from the 2007 stewardship fishery were 2364 t. This included 2192 t taken as directed catch and 172 t as by-catch. In addition, 182 t were landed in the sentinel surveys. The offshore portion of the stock area remained closed to directed fishing.
• Two estimates of landings from recreational fisheries in 2007 were available. One suggested a recreational catch that was comparable to the stewardship fishery catch; the other suggested the recreational catch was much lower (371 t).
• Until recreational catch is determined, total catch is uncertain. Without a reliable estimate of total catch, a sequential population analysis could not be conducted.
• Total mortality in the offshore was extremely high during 1996-2003 and has been a major impediment to stock recovery. Total mortality has declined substantially since 2003.
• Based on autumn and spring surveys, the average biomass of cod in the offshore over the last 3 years is 4-5% of the average during the 1980’s. However, survey biomass has been increasing since 2003.
• The recent increase in offshore biomass is mostly due to improved survival and the continued growth of the 2002 year-class, and the appearance offshore after 2005 of the 2000-2001 year-classes.
• Recruitment in the offshore has been weak since the 1989 year-class and has subsequently varied without trend.
• The moratorium on directed fishing in the offshore should be continued, and by-catch should be minimized.
• The industry telephone survey conducted during 2007 showed most harvesters in 2J3KL felt that cod were more abundant during 2007 than during 2006.
• For assessment purposes the inshore was divided into three areas: 1) a northern area (2J and northern 3K); 2) a central area (southern 3K and northern 3L) where most of the resident inshore fish are located; and 3) a southern area (southern 3L) that is largely dependent on migrant fish, from 3Ps and possibly other offshore areas.
• In the inshore northern area, sentinel catch rates were low in 1995-2004, increased in 2005, and are currently above the average of the time series. Stewardship fishery catch rates in 2006-07 were slightly higher than in earlier fisheries during 1998-2002.
• In the inshore central area, sentinel catch rates have generally increased since 2002 and are currently above the average of the time series. Stewardship fishery catch rates in 2006-07 were higher than in earlier fisheries during 1998-2002.
• In the inshore southern area, sentinel catch rates have remained stable since 2003, but are below the average of the time series. Stewardship fishery catch rates in 2006-07 were similar to those in earlier fisheries during 1998-2002.
• Catch rates in the inshore northern area and inshore southern area have been lower than those in the inshore central area since 2002, suggesting lower cod densities in these areas.
• In the inshore central area, a pre-recruit index suggests that the strength of the 2003-2006 year-classes will be much lower than those that have supported recent fisheries. Sentinel small-mesh gillnet catch rates also suggest the 2003-2004 year-classes are weak; the 2005 and 2006 year-classes are not yet sampled by this gear.
• During 2007, mean annual exploitation rates from tagging studies were consistently low among inshore central and southern areas, ranging from 6 – 7%.
• The inshore northern area is primarily dependent on seasonal immigration of fish, possibly from the offshore. Therefore it is recommended to minimize removals from this area.
• In the inshore central area the exploitable biomass has increased recently, as inferred from trends in catch rates. However, due to the weaker 2003-2006 year-classes, this increasing trend may not continue. The impacts on stock growth of fishing at specific catch levels could not be quantified.
• The inshore southern area is primarily dependent on seasonal immigration of fish, the magnitude of which cannot be predicted. Therefore, the effect of removals of various levels cannot be estimated.
• There is a risk that fishing inshore will impede stock growth offshore. The level of risk is difficult to quantify, but exploitation rates inshore are currently low and offshore biomass is increasing.
• If exploitation rates inshore increase then the risk of fishing inshore on stock growth offshore may increase.

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