Southern Gulf of St. Lawrence, NAFO Division 4T, Sea Scallop (Placopecten magellanicus) Stock Assessment to 2023

Abstract

Status The exploitable biomass estimate of the southern Gulf of St. Lawrence (sGSL) Sea Scallop stock is in the Critical Zone of the Precautionary Approach (PA) Framework and has a very high (greater than 99%) probability of being in the Critical Zone. Trends Initial biomass of the sGSL Sea Scallop stock was high (~4,000 tonnes of meat weight, t) prior to the onset of commercial fishing and rapidly declined below the limit reference point (LRP) over a period of approximately 10 years; biomass has remained stable below the LRP since 1982. Biomass estimates have shown a slight increase toward the LRP in the last three years (2021-2023). Recruit numbers peaked in 2021 for the survey time series (2019-2023). Clapper index (proxy of natural mortality) has also been increasing in recent years. Ecosystem and Climate Change Considerations Because Sea Scallops are mostly sedentary molluscs, the sGSL Sea Scallop stock is susceptible to climate change stressors. Sea Scallops are vulnerable to temperatures exceeding 21 °C. Maximum summer bottom temperatures in the Northumberland Strait have increased steadily since 1995. The number of days exceeding 21 °C per year has also been increasing. Stock Advice The estimated biomass of the sGSL Sea Scallop stock dropped below the LRP in 1982 and has remained there since. Stock projections are not available.