Research Document 2024/020
Framework Assessment of the American Lobster (Homarus americanus) Stock Status in the Southern Gulf of St. Lawrence (LFAs 23,24, 25, 26A and 26B)
By Asselin, N.C., Surette, T., Gagnon, D., Boudreau, S.A. and Chassé, J.
Abstract
Active for more than a century, the American Lobster fishery in the southern Gulf of St. Lawrence (sGSL) has seen varying levels of productivity over this time period. This framework presents indicators of abundance, productivity, fishing pressure and the environment, to be used in future stock assessments. Abundance indicators include landings, Catch per Unit Effort (CPUE), commercial biomass and commercial abundance. These multiple indicators from different data sources show a consistent trend of increasing Lobster abundance since the previous assessment. Indicators of productivity, including pre-recruit CPUE, pre-recruit abundance, juvenile density, young-of-year density and egg production, are positive but the densities of small benthic Lobsters appear to be stabilizing (i.e. juveniles and young-of-year). For fishing pressure, the percent empty traps has decreased while exploitation rates appear stable, indicating that the stock can likely sustain current levels of exploitation. For habitat indicators, reduced Rock Crab densities within the prey availability indicator may be a result of high Lobster abundance. A substantial reduction in the predator pressure indicator has occurred since the 1970s, but the effects of this reduction on the Lobster stock were not evaluated. In terms of seafloor temperature, available Lobster habitat has increased in June in the sGSL since 1985.
Total landings of 39,313 tonnes (t) in 2021 in the sGSL were well above the Limit Reference Point (LRP, 6,899 t), the Upper Stock Reference (USR, 13,798 t) and the Biomass at Maximum Sustainable Yield (BMSY, 17,247 t), placing the stock within the defined healthy zone of the precautionary approach. Changes in Lobster abundance, and observed concurrent changes in the populations of other commercially fished species in the sGSL, may indicate a regime shift. Re-evaluation of the LRP could be considered to ensure it reflects the current ecosystem. The use of fishery-independent data to establish the LRP would be preferable, to remove uncertainty related to changes in the fishery.
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