Research Document 2024/076
Scallop Fishery Assessment of the Southern Gulf of St. Lawrence to 2023: Commercial Fishery and Survey Data
By Niles, M., Harbicht, A., Barrell, J., Clements, J.C., Sonier, R.
Abstract
The 2024 sea scallop stock assessment for the southern Gulf of St. Lawrence (sGSL) incorporates data from the commercial fishery (1923-2023) and research surveys (2019-2023). We present landings, effort and catch rates (CPUE) at the Scallop Fishing Area (SFA) level, the bed level, and the core area (SFAs 22 and 24) level for the available time series.
Annual landings in the sGSL were 69 tonnes (t) in 2022 and preliminary landings 83 t in 2023, averaging 75 t since 2017, with the majority (94%) originating from the core area, specifically, SFAs 22 (59%) and 24 (35%). Spatial analysis of logbooks revealed that approximately 61% of core landings were from the three major beds: West Point and Cape Tormentine in SFA 22 and Pictou in SFA 24. Commercial catch rates for the core area averaged 6.6 kg h-1 (8.09 kg h-1 and 5.24 kg h-1 for SFAs 22 and 24, respectively), higher than the rates reported in the previous assessment. In fact, catch rates in 2023 were the highest in the time series (2003 to 2023). A depletion model was fit to landings and catch rate data from 2003 to 2023, revealing high exploitation rates for the two major scallop beds in SFA 22 (average 50%), suggesting overfishing. The failure to fit the model to SFA 24 data highlights uncertainties in fishery-dependent data. Logbook accuracy and completeness remain critical for reliable assessments and science advice.
Annual research surveys were initiated in 2019 to build a time series of data for the major scallop beds in the sGSL. Condition monitoring on these same beds during the fishery began in 2021. Survey biomass indices increased by 26% and 22% from 2022 to 2023 for West Point bed and Cape Tormentine bed, respectively, while commercial scallop numbers increased only by 5%. The biomass index remained relatively stable for the Pictou bed at around 36 t and the survey index for commercial scallop numbers decreased by 10%, from 2022 to 2023. Recruit numbers peaked in 2021 in Cape Tormentine bed. Higher biomass indices for the West Point and Cape Tormentine beds (SFA 22) in 2023 coincided with higher (≈18%) condition and fishery catch rates observed that year. Strong cohorts of small scallops were observed on Pictou bed in 2023. Survey estimates of exploitable biomass before the fishery and prorated for the core area ranged between 250 t and 390 t. Survey exploitation rate indices on the core area averaged 24% for the time series.
According to the updated JABBA model, using commercial catch and CPUE up to 2023, as well as research survey biomass indices, biomass levels for the core sGSL sea scallop stock have been relatively constant around 250 t since the late 1990s to 2021 when the levels begin to increase, reaching 300 t by 2023. Applying the 0.4 BMSY recommendation from the Precautionary Approach framework results in a limit reference point (LRP) for the core sGSL sea scallop stock of 556 t. Biomass estimates for 2021, 2022 and 2023 indicate the sGSL stock is currently below this LRP, and removals need to be kept to a minimum as this level of abundance places the stock in the Precautionary approach’s Critical zone. Consequently, a rebuilding plan to bring the scallop stock above the LRP will be required within two years.
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