Science Advisory Report  2009/047

Assessment of the lobster populations of the North Shore (LFAs 15, 16 and 18) and Anticosti Island (LFA 17) in 2008

Summary

• Lobster landings on the Lower North Shore in LFAs 15 and 16 have been dropping since the early 2000s. They dropped from 38 to 14 tons and from 11 to 5 tons between 2000 and 2008 respectively. Landing data may be somewhat partial however. The fishing effort index has also dropped over the same period. Only a small proportion of the authorized fishing effort is being deployed. Landings from Anticosti Island (LFA 17) increased from 87 tons in 2004 to 151 tons in 2008, after a sharp decrease period (50%) from 1999 to 2004.
• Catch rates from sampling at sea and dockside were weak but stable in LFAs 15 and 16 between 1983 and 2008, averaging 0.3 lobster/trap and 0.17 kg/trap. At Anticosti Island, the catch rates recorded in logbooks were slightly higher from 2006 to 2008 (0.68 kg/trap on average) than in 2004 (0.54 kg/trap). Overall, they seem to be lower on the north side of the island.
• In LFAs 15 and 16, the mean size (carapace length, CL) of commercial lobster has continued to increase, even after 2005 when the minimum legal size increase had ended (92.4 mm CL in 2008 and 91.1 mm CL in 2005). Size structures were less truncated from 2005 to 2008 than in 2004, suggesting a drop in the exploitation rate. As opposed to 2004, jumbo lobster (≥ 127 mm CL) were observed, although their proportion was weak (<1 %). The sex-ratio was in favour of males and appears suitable for reproduction.
• At Anticosti Island, the size structures of lobster were characterized by the occurrence of large individuals. The structures observed over the last 3-4 years suggest an improvement compared to 2004, when a significant drop in the number of large individuals had been recorded. In 2008, the size structure showed several modes, suggesting a relatively low exploitation rate. The proportion of jumbos (≥ 127 mm CL) increased from 2% in 2004 to 7% in 2008. The sex-ratio was in favour of males and appears suitable for reproduction.
• Lobster populations on the Lower North Shore and Anticosti Island are near the species’ northernmost range limit. They are characterized by slow growth and late sexual maturity (92-94 mm CL). These populations are likely more vulnerable to over-harvesting because of lower productivity compared to other areas further south and possibly exacerbated by a colder environment over the last few years. Therefore, it is important to maintain low exploitation rates. It would also be important if the minimum legal size was closer to the size at sexual maturity because in the current context, the fishery also harvests immature lobster.

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