Research Document 2024/069
Stock Assessment of Atlantic Surfclam (Spisula solidissima) of the Îles-de-la-Madeleine in 2023
By Gianasi, B. L. and Desrosiers, B.
Abstract
Quebec’s Atlantic surfclam fishery is confined to the Îles-de-la-Madeleine. Commercial fishing is carried out from vessels in coastal waters using hydraulic clam dredges or by hand harvesting, either by digging by hand or by diving in lagoons and along the coast. Hand harvesting is well established in both the recreational and commercial fisheries in the Îles-de-la-Madeleine. However, the scope of recreational harvesting on the islands is poorly known.
Three surfclam beds were delineated in sub-areas 5A1 and 5B1 based on the location of commercial dredging. The Chenal de la Grande-Entrée (CGE) and East beds are in sub-area 5A1, while the North bed straddles sub-areas 5A1 and 5B1. The fishery initially exploited the CGE and East beds, but expanded to the North bed when the latter was discovered in the 2000s. From 2012 to 2018, the fishery was concentrated mainly in the North bed, but resumed in the CGE bed in 2019. From 2021 to 2023, the fishery operated in both the North and CGE beds.
The total allowable catch (TAC) has not been reached in sub-areas 5A1 and 5B1 since 2019, and average landings in 2021–2023 (177 t) remained below the historical average (193 t, 2002–2020). The decline in landings is partly due to the fluctuating number of active harvesters (between two and four) in recent years. When the fishery resumed on the CGE bed in 2019, the non-standardized catch per unit effort (CPUE) was high (337 kg/h·m). The average for the last three years (232 kg/h·m) is still above the historical average (176 kg/h·m, 2002–2020), but shows a downward trend. The CPUE for the North bed was high in 2021 (330 kg/h·m), but has been falling since then, and the 2021–2023 average (215 kg/h·m) is slightly below the historical average (233 kg/h·m, 2002–2020). Although the size of landed surfclams has remained stable (130 mm), exceeding the minimum legal size of 90 mm, the drop in landings and CPUE values in recent years suggests that removal rates may be too high in sub-areas 5A1 and 5B1.
Landings from commercial hand harvesting (dive fishing and hand digging) varied with the fishing effort. Non-standardized CPUEs in the dive fishery were slightly above the reference mean in sub-area A-12.1, but below it in A-9.5. For onshore harvesting (i.e., hand digging), CPUEs in A-09.5 increased relative to their respective historical means. The average size of landed clams was around 130 mm for dive harvesting and 120 mm for onshore harvesting.
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