Science Advisory Report 2010/029
Assessment of the Estuary and Northern Gulf of St. Lawrence (Areas 13 to 17, 12A, 12B, 12C and 16A) Snow Crab Stocks in 2009
Summary
- Generally, in 2009, stocks in the Estuary and northern Gulf of St. Lawrence were characterized by a stable or slightly decreasing commercial biomass. Lower North Shore stocks (15-14-13-12C and 16A) were mostly made up of intermediate-shell crab, whereas stocks further west or in the south (16, 17, 12A) had a significant proportion of recruits. The accumulated biomass available to the fishery in 2010 is highly variable according to the stocks. It is low for some stocks that seem to be nearing a recruitment trough while it remains high for others. Area 16 is an exception as it seems to be nearing a recruitment trough despite presenting a high abundance. Recommendations for 2010 are status quo in terms of TAC in all areas except for Area 13. The status quo promotes stock stability where the TAC has already been adjusted downward as a result of lower biomass, or in other cases, provides for moderate exploitation of stocks that still have a high accumulated biomass, although it may be decreasing, before an overly large quantity is lost to commercialization or reproduction.
- Advices for 2010 encourage the maintenance of an adequate reproductive biomass for males so as to not adversely affect the recovery or maintenance of the population in a given area. Recommendations assume that the natural mortality rate will not differ in 2010 compared with previous years.
The status quo with 2009 is recommended for the TAC in 2010 in Areas 17, 16, 15, 14, 12A, 12B, 12C and 16A:
In Area 17, the TAC decrease between 2006 and 2008 provided some stability in terms of catch rates. However, the predominance of recruits in the landings suggests that the exploitation rate is high. Recruitment could remain at a similar level as in 2009 over the next 2-3 years.
In Area 16, the relative stability of the catch rates in the postseason survey and the predominance of recruits in the landings suggest that the exploitation rate should not be increased in 2010. Recruitment outlooks over the medium term are positive which will help maintain a relatively high biomass.
In Area 15, the accumulated commercial biomass appears to be relatively high and based on the postseason survey results, it was comparable in 2009 and 2008, which suggests that the same fishing pressure can be maintained without causing any negative impact on the 2010 stock. Indicators do not suggest any significant recruitment over the next 2-3 years.
In Area 14, the stock appears to show a certain balance between sampling and recruitment since 1999. Recruitment to the fishery has not been high enough since 1999 to generate a significant increase in available commercial biomass, except for 2003 when the TAC was significantly reduced. However, the high proportion of intermediate-shell crab in the landings since 1999 suggests that the exploitation rate has not been excessive.
In Area 12A, the TAC decrease from 2005 to 2008 has led to some stabilization in catch rates but at a low level, suggesting that the exploitation rate should not be increased. Indicators do not suggest significant recruitment for 2010.
In Area 12B, although the catch rate has been stable for several years, the gradual increase in the proportion of recruits in the landings, and the percentage of recruits observed in the postseason survey of 2009 suggests a growing dependence of the fishery on recruitment. In this context, the exploitation rate should not be increased in 2010.
In Area 12C, stock status has been relatively stable since 1997. Various indicators suggest some stability for 2010 and the presence of a high proportion of intermediate-shell crab in the landings suggests that the exploitation rate was not excessive in 2009. There are four adjacent areas to Area 12C which were also somewhat stable and where quotas similar to 2009 have been recommended.
In Area 16A, the brief historical series of the commercial fishery and postseason surveys do not provide much context for interpreting the catch rate declines observed in 2009. Given 1) the stability in the four neighbouring areas, on which Area 16A is partially dependent and 2) the high proportion of intermediate-shell crab in the landings from Area 16A, suggesting a moderate exploitation rate, the quota can be maintained at the same level as in 2009.
In Area 13, following the step-by-step approach adopted upon the reopening of the area in 2008, a TAC increase of 25%, of 185 t in 2010 and 2011 is recommended. The predominance of intermediate-shell crab in the landings from Area 13 suggests that the exploitation rate was not excessive in 2008 and 2009.
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