Science Advisory Report 2023/027

Assessment of the Estuary and northern Gulf of St. Lawrence (Areas 13 to 17, 12A, 12C and 16A) snow crab stocks in 2022

Summary

Area 17

• The total allowable catch (TAC) in 2022 was similar to that in 2021 (1,202.8 t, down 0.9%), and was reached. Landings in 2022 totalled 1,211.6 t, representing a 0.4% decrease from 1,217.0 t in 2021.
• Between 2021 and 2022, the standardized commercial catch per unit effort (CPUE) declined slightly (-2.5%) and is currently below the historical average [2000; 2021].
• The carapace width of legal-size crabs sampled at sea increased between 2021 and 2022, and is above the historical average [2000; 2021].
• According to dockside sampling data, recruits made up more than half of landings in 2022, a trend observed since 2018.
• The commercial abundance index derived from the post-season survey rose significantly between 2021 and 2022 and is slightly below the historical average [2000; 2021]. This increase is observed throughout the fishing area, with recruit abundance above the historical average [2000; 2021]. The abundance of legal- and sublegal-size adolescent males declined in the southern part of the fishing area but increased in the northern part—in both cases, to below the respective historical average [2000; 2021].
• According to the post-season survey, the abundance of primiparous females has been increasing since 2020, while the spermathecal load weight has been decreasing since 2019.
• Indicators of favourable thermal habitat for large and small crabs showed a downward temporal trend during the 1990-2022 period.
• The combined index, derived from the commercial CPUE and the number per unit effort (NPUE) obtained from the post-season survey, rose by 26.6 % in 2022, suggesting that the biomass available to the fishery in 2023 will be greater than in 2022.

Outlook

• The combined index increased between 2021 and 2022, suggesting that the biomass available to the fishery in 2023 will be greater than that in 2022.
• Given the expected high abundance of recruits, associated with densities of mature females that are still high, it is suggested that the increase in removals in 2023 be limited to prevent increased white crab mortality and to avoid obtaining a sex ratio that is overly biased towards females.

Higher scenario: A 25% increase relative to total landings in 2022.

Intermediate scenario: A 15% increase relative to total landings in 2022.

Lower scenario: A 5% increase relative to total landings in 2022.

Area 16

• The total allowable catch (TAC) in 2022, which was increased to 2,236.9 t from 2021, was reached. Landings in 2022 totalled 2,252.0 t (+14.7% between 2021 and 2022).
• The standardized commercial catch per unit effort (CPUE) increased in 2022 (+9.8%) for the third consecutive year, and is slightly below the historical average [1996; 2021].
• The carapace width of legal-size crabs sampled at sea was down slightly, but is close to the historical average [1996; 2021].
• According to dockside sampling data, crabs with a carapace condition of 1-2 (recruits) made up roughly one half of landings in 2022, a proportion that has been fairly stable since 2019.
• According to the 2022 post-season survey, the abundance indices for both adult and adolescent males increased between 2021 and 2022, with a marked increase in sub-legal size adults. The mean carapace width of adult and adolescent male crabs caught in this survey with standard traps declined and is below the historical average [1996; 2021].
• The abundance of females in the post-season survey is still high in the western part of the area.
• According to the data obtained in the 2022 scientific trawl survey in Sainte-Marguerite Bay, primiparous female recruitment will likely decrease over the next few years, while recruitment to the commercial fishery should increase. However, the average size of adult males is declining and early terminal moulting (i.e. before crabs reach legal size) is increasingly frequent, representing significant losses for the commercial fishery, particularly from 2019 to 2022.
• The indicators of favourable thermal habitat for large and small crabs showed a downward temporal trend over the period [1990; 2022].
• The combined index, derived from the commercial CPUE and the number per unit effort (NPUE) obtained from the post-season survey, increased for a second year (+23.1%), suggesting that the biomass available to the fishery in 2023 should be greater than in 2022.

Outlook

• The combined index increased between 2021 and 2022 (+23.1%), which suggests that the biomass available to the fishery in 2023 should be greater than in 2022.
• Given the expected high abundance of recruits, associated with densities of mature females that are still high, it would be a good idea to limit the increase in removals in 2023 to prevent increased white crab mortality and to avoid obtaining a sex ratio that is overly biased towards females.

Higher scenario: A 25% increase relative to total landings in 2022.

Intermediate scenario: A 15% increase relative to total landings in 2022.

Lower scenario: A 5% increase relative to total landings in 2022.

Area 15

• In 2022, the total allowable catch (TAC) was reduced to 243.2 t, representing a 25.3% decrease relative to 2021, and was fully fished. Landings in 2022 totalled 237.0 t, a 22.5% decline from 306.0 t in 2021.
• The commercial catch per unit effort (CPUE) declined between 2021 and 2022 ( 6.8%). The values in the last four years are the lowest for the period [2000; 2022].
• The carapace width of legal-size crabs sampled at sea is decreasing and is currently below the historical average [2000; 2021].
• According to dockside sampling data, recruits made up slightly over half of landings in 2022, a proportion that has been increasing since 2019.
• All abundance indices obtained from the post-season survey showed an upward trend between 2021 and 2022 for both adolescent and adult males, and the 2022 values were above their respective historical averages [2014; 2021]. The mean carapace width of adult and adolescent male crabs caught with standard traps, which has fallen below the historical average between 2017 and 2020, has increased since 2020 but remains below the historical average [2000; 2021].
• The experimental traps used in the post-season survey indicate a high density of primiparous females in the last four years. All indicators point to increasing levels of recruitment to the commercial fishery, and this trend is expected to continue in the short and medium term.
• The combined index, derived from the commercial CPUE and the number per unit effort (NPUE) from the post-season survey, increased sharply between 2021 and 2022. This suggests that the biomass available to the fishery in 2023 should be greater than that in 2022.

Outlook

• The combined index, which had declined to one of the lowest values recorded since 2014, increased sharply between 2021 and 2022, due to a significant increase in the abundance of commercial-size crabs—which consisted of recruits and crabs left by the fishery in equal proportions—in the 2022 post-season survey. The biomass available to the fishery in 2023 is expected to be greater than that in 2022.
• Since CPUE values from the last four years were the lowest in the time series, caution is recommended in increasing removals.

Higher scenario: A 45% increase relative to total landings in 2022.

Intermediate scenario: A 35% increase relative to total landings in 2022.

Lower scenario: A 25% increase relative to total landings in 2022.

Area 14

• In 2022, the total allowable catch (TAC) was reduced to 309.9 t, a 15.1% decrease in relation to 2021, and was reached. Landings in 2022 totalled 310.7 t, down 14.3% from 362.5 t in 2021.
• Between 2021 and 2022, the commercial catch per unit effort (CPUE) increased by 20.2%, remaining slightly below the historical average [2000; 2021].
• The carapace width of legal-size crabs sampled at sea decreased and is below the historical average [2000; 2021].
• According to dockside data, landings in 2022 primarily consisted of intermediate-shell crabs, followed closely by recruits.
• According to the post-season survey data, the abundance of adult legal-size male crabs increased between 2021 and 2022, due to an increase in the number of commercial crabs left by the fishery. Recruit abundance declined during the same period. The average size of adult male crabs caught with standard traps has been declining since 2016 and is below the historical average [2000; 2021], while the abundance of adult sublegal-size males increased sharply between 2021 and 2022. The abundance of primiparous and multiparous females is declining, while the spermathecal load weight is increasing.
• The 2022 scientific trawl survey conducted in the eastern part of Areas 13 and 14, in the Lower North Shore area, points to a high density of primiparous and multiparous females and sublegal-size males.
• The combined index, derived from the commercial CPUE and the number per unit effort (NPUE) from the post-season survey, rose sharply between 2021 and 2022, indicating that the biomass available to the fishery will likely be greater in 2023 than in 2022.

Outlook

• The combined index rose sharply between 2021 and 2022, indicating that the biomass available to the fishery in 2023 should be greater than in 2022 and consist mainly of crabs left by the fishery.
• In light of the decline in the abundance of recruits and legal-size adolescents observed in the 2022 post-season survey, it is recommended that caution be exercised when increasing removals.

Higher scenario: A 35% increase relative to total landings in 2022.

Intermediate scenario: A 25% increase relative to total landings in 2022.

Lower scenario: A 15% increase relative to total landings in 2022.

Area 13

• Between 2021 and 2022, the total allowable catch (TAC) decreased by 18.7% to 198.3 t, and was reached. Landings in 2022 totalled 188.0 t, down 5.5% from 199 t in 2021.
• Between 2021 and 2022, the commercial catch per unit effort (CPUE) increased by 45.5% and is currently below the historical average [2000; 2021].
• Dockside sampling of legal-size crabs showed a decrease in the carapace width between 2021 and 2022 to values below the historical average [2000; 2021]. The 2022 values are at 2002 pre-moratorium levels.
• According to the dockside sampling data, landings consisted primarily of recruits for the second consecutive year.
• The commercial abundance index derived from the post-season survey rose between 2021 and 2022 and is now above the average for the last three years [2019; 2021]. This upward trend reflects the increasing abundance of recruits in the northern part of the fishing area. The average size of adult males caught with standard traps has been declining since 2016 and is below the historical average [2000; 2021]. The abundance of sublegal-size adult males rose significantly in the northern part of the area between 2021 and 2022. The abundance of primiparous and multiparous females declined, while the spermathecal load weight increased.
• The 2022 scientific trawl survey in the eastern part of Areas 13 and 14, in the Lower North Shore, points to a high density of primiparous and multiparous females and sublegal-size males.
• Between 2021 and 2022, the combined index, derived from the commercial CPUE and the number per unit effort (NPUE) from the post-season survey, increased sharply. The biomass available to the fishery in 2023 is expected to be greater than that in 2022.

Outlook

• Between 2021 and 2022, the combined index increased. The biomass available to the fishery in 2023 is expected to be greater than that in 2022.
• Given the reliance of the commercial fishery on recruits and the smaller carapace width of the crabs caught in the post-season survey, it is suggested that caution be exercised in setting the TACs during the resumption of the recruitment pulse to prevent increased white crab morality.

Higher scenario: A 20% increase relative to total landings in 2022.

Intermediate scenario: A 10% increase relative to total landings in 2022.

Lower scenario: Status quo relative to total landings in 2022.

Area 16A

• The total allowable catch (TAC) remained the same in 2021 and 2022, at 245 t, and was fully fished in 2022, with landings of 244.3 t.
• The commercial catch per unit effort (CPUE) increased between 2021 and 2022 (+33.9%), although the 2022 value remained below the historical average [2002; 2021].
• The carapace width of legal-size crabs sampled at sea has remained stable since the last time sampling took place (2019), and is still above the historical average [2002; 2019].
• According to dockside sampling data, recruits have accounted for slightly over half of landings since 2018.
• According to the 2022 post-season survey data, the abundance of legal-size crabs, which primarily consist of recruits, is increasing. Although the abundance of crabs left by the fishery increased between 2021 and 2022, it still remains very low. The mean carapace width of male crabs caught in this survey with standard traps declined, and was below the historical average [2002; 2021].
• Data from the experimental traps used in the post-season survey indicate a high density of primiparous females in the last four years. According to all the indicators, recruitment to the commercial fishery is likely increasing and this is expected to continue over the short and medium term.
• The indicator of favourable thermal habitat for small crabs showed an upward temporal trend during the 1990-2022 period, while that for large crabs declined slightly during the same period.
• The combined index, derived from the commercial CPUE and the number per unit effort (NPUE) from the post-season survey, increased for the first time since 2014. The large increase between 2021 and 2022 suggests that the biomass available to the fishery in 2023 will be greater than in 2022.

Outlook

• The combined index, after declining during the 2014-2021 period, rose sharply between 2021 and 2022, suggesting that the biomass available to the fishery will increase in 2023. However, commercial fishery yields are still low and the abundance of crabs left by the fishery was very low.
• Given the commercial fishery’s reliance on recruits, caution should be exercised in increasing removals during the resumption of the recruitment pulse, to prevent increased white crab mortality.

Higher scenario: A 30% increase relative to total landings in 2022.

Intermediate scenario: A 20% increase relative to total landings in 2022.

Lower scenario: A 10% increase relative to total landings in 2022.

Area 12C

• The total allowable catch (TAC) in 2022 was reduced to 71.5 t from 2021, and was not reached. Landings in 2022 totalled 66.0 t.
• The commercial catch per unit effort (CPUE) increased between 2021 and 2022 (+17.1%), but the 2022 value remains among the lowest in the time series [2001; 2021].
• The carapace width of legal-size crabs sampled at sea increased, but remained below the historical average [2001; 2021].
• According to dockside sampling data, the proportion of recruits increased between 2021 and 2022. In 2022, landings were made up mostly of recruits.
• Different spatial coverage in the post-season surveys created some uncertainty in the indicators for 2021 and 2022. The difference in NPUE95 (legal-size adults) between 2021 and 2022 was +42.5% without adjusting for the differences in the protocol, but 23.7% when the transects sampled in the two years were compared. The abundance of commercial-size adults in 2022 remained very low. The mean carapace width of male crabs caught in the post-season survey with regular conical traps is stable, but below the historical average [2001; 2021].
• The indicator of favourable thermal habitat for large crabs showed a downward temporal trend during the 1990-2022 period.
• The value of the combined index, derived from the commercial CPUE and the number per unit effort (NPUE) from the post-season survey, in 2022 was among the lowest observed since the time series began in 2014.

Outlook

• Given the uncertainty created by the difference in the spatial coverage in the post-season surveys in 2021 and 2022, the combined index will not be used as the main reference for recommendations.
• Standardized CPUE values increased by 17.1% between 2021 and 2022, while the difference in NPUE95 values between the two years was calculated at 23.7%, based on the transects sampled in the two years. The biomass available to the fishery in 2023 could remain at a level similar to that in 2022.
• Given the heavy reliance of the commercial fishery on recruits and the smaller carapace width of the crabs caught in the post-season survey, caution should be exercised in setting the TACs during the resumption of the recruitment pulse.

Higher scenario: A 10% increase relative to total landings in 2022.

Intermediate scenario: Status quo relative to total landings in 2022.

Lower scenario: A 10% decrease relative to total landings in 2022.

Area 12A

• In 2022, the total allowable catch (TAC) was reduced to 43.1 t, representing a 37.5% decrease relative to 2021, and was fully fished. Landings in 2022 totalled 43.0 t, a 20.4% decline from 54.0 t in 2021.
• The commercial catch per unit effort (CPUE), which reached its lowest value in the time series in 2021, increased in 2022 and is below the historical average [2001; 2021].
• The carapace width of legal-size crabs sampled at sea and at dockside was down between 2021 and 2022 and is below the historical average [2001; 2021].
• According to dockside sampling data, intermediate-shell crabs made up more than half of landings in 2022, a trend observed since 2004.
• According to the post-season survey data, the commercial abundance index increased between 2021 and 2022, after a steady decline since 2011, but remains among the lowest in the time series [2001; 2021]. The abundance of primiparous females remains high in 2022.
• Indicators of favourable thermal habitat for large crabs showed a downward temporal trend during the 1990-2022 period.
• The combined index, derived from the commercial CPUE and the number per unit effort (NPUE) from the post-season survey, reached its lowest value in 2021 and is increasing between 2021 and 2022, indicating that the biomass available to the fishery will likely be greater in 2023 than in 2022.

Outlook

• The combined index, which reached its lowest value in 2021, increased between 2021 and 2022, suggesting that the biomass available to the fishery in 2023 will be greater than that in 2022.
• However, the biomass and abundance indices are at very low levels. In addition, the density of mature females is still high. All the indicators point to the need to exercise caution when establishing harvest levels for 2023.

Higher scenario: A 10% increase relative to total landings in 2022.

Intermediate scenario: Status quo relative to total landings in 2022.

Lower scenario: A 10% decrease relative to total landings in 2022.

This Science Advisory Report is from the regional peer review meeting of February 15-17, 2023 on the Assessment of the Estuary and northern Gulf of St. Lawrence Snow Crab stocks (zones 12A, 12C, 13, 14, 15, 16, 16A and 17). Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

Science Advisory Report 2023/027 (PDF, 1,748 KB)

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