SFA 27A (Georges Bank 'a') Sea Scallop (Placopecten magellanicus) Stock Assessment in 2024

Abstract

Status The median fully-recruited biomass estimate in 2024 was 13,570 t (meats), with 0.76 probability of being above the upper stock reference (USR) and in the healthy zone. The median recruit biomass estimate in 2024 was 1,391 t, which is below the long-term median (1986–2023) of 3,428 t. In 2024 the estimated proportional exploitation rate (0.18) was below the removal reference (RR) of 0.25. Trends Fully-recruited biomass has fluctuated within the healthy zone since the 2000s. Fully recruited biomass decreased by 56% from 31,095 t in 2023 to 13,570 t in 2024. Recruit biomass fluctuated above the long-term median from 2008 to 2018, and has decreased since the historically high recruitment event in 2009. Recruit biomass was below the long-term median in 2024 and decreased by 72% from 2023. The estimated proportional exploitation rate has fluctuated below the RR since 2006. Exploitation increased in 2024 but was comparable to the past 20 years. The estimated natural mortality rates for both recruit and fully-recruited scallop have increased since 2019. In 2024, the estimated natural mortality of both size classes increased to 0.41, approaching the highest values observed in their respective time series. In 2024, scallop condition declined by 39% compared to 2023 and was below the long-term median. The decline from 2023 to 2024 was the largest decline in scallop condition between subsequent years in the time series. Ecosystem and Climate Change Considerations Research vessel survey data from Canada and the United States suggest that predator abundance, notably sea stars (Asterias spp.) and crabs (Cancer spp.), has increased within areas of known scallop distribution. Aggregations of predators in areas of high scallop density contribute to increases in natural mortality. Observations of significant interannual changes in scallop condition in SFA 27A are likely driven by environmental variability. Stock Advice Based upon preliminary analysis of the 2024 fishery and DFO Maritimes Offshore Scallop survey data, an interim total allowable catch (TAC) of 2,100 t (meats) was set for the 2025 SFA 27A fishery. A catch of 2,100 t would result in an expected 37% decrease in fully-recruited biomass. The probability that a catch of 2,100 t will result in the fully-recruited biomass remaining above the LRP is 0.93 and the probability remaining above the USR is 0.18. Catch of 2,100 t is estimated to result in an exploitation rate of 0.25 which is at the RR (0.25).