Science Advisory Report 2009/013

Assessment of lobster stocks of the Magdalen Islands (LFA 22) in 2008

Summary

• The abundance indicators remained generally high from 2006 to 2008. Landings have increased from 2,341 t in 2005 to 2,492 t in 2008. In 2008, they were 20% higher than the average over the last 25 years (2,082 t). The mean catch per unit effort (CPUE) for commercial lobsters was relatively stable from 2006 to 2008, at 0.7 lobster/trap and 0.4 kg/trap, but dropped by about 7% compared to 2005. In 2008, even though the CPUE in numbers was 12% lower than the 1985-2007 series average, it was about 4% higher in weight.
• The demographic indicators showed that the average size of lobster caught has been stable since 2003 at a level about 6-7 mm larger (carapace length, CL) than the mean size recorded prior to the increase of the minimum legal size, and a mean weight of about 25% higher. From 2005-2008, the sex-ratio remained in favour of males overall and seems appropriate for reproduction. Size structures were truncated and consequently, the proportion of jumbo size lobster (≥ 127 mm CL) remained low (< 1%), but slightly increased nevertheless from 2005-2008.
• The fishing pressure indicators revealed that the estimated exploitation rates for 2005 to 2007 varied between 71 and 77% in the south and between 69 and 71% in the north, compared with 74% in 2004. However, fishing mortality for the portion of the population ≥ 76 mm CL dropped as a result of the increase in the minimum legal size.
• The stock productivity indicators remained positive from 2006 to 2008. The abundance of berried females has remained higher than prior to the increase of the minimum legal size, despite a drop in their CPUE in 2008. As in 2005, egg production estimates for 2006-2008 were higher by a factor of around two compared to those prior to the increase of the minimum legal size. In 2008, the number of multiparous females was slightly higher than in 2005 and their relative contribution to the total egg production was also higher. Recruitment indices recorded in 2008 suggest that the 2009 landings could remain high. The juvenile abundance indices also suggest there could be a good recruitment to the fishery in the medium term.
• Despite the efforts and positive signs, some improvements to the size structure of the stocks appear necessary. This will help reduce the dependence of the fishery on the annual recruitment and will also help increase the proportion of multiparous females in the population and ensure their reproductive success by maintaining suitable sex-ratios, according to the recommendations by the FRCC (2007). Thus, it is important to continue the program for reducing the fishing effort introduced in 2006. In a long term outlook, it is important to identify some biological reference points in developing a formal precautionary approach for this fishery.

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