The toothfish fishery in the Amundsen Sea region operates under a research plan developed by the Scientific Committee in 2014, designed to provide data to support a two-area stock assessment model. An uneven distribution of fishing effort on the seamounts in the north of this region (included within Small-Scale Research Unit 88.2H) has had an impact on the tagging programme and limited recapture data. This issue has been compounded by fewer vessels fishing in the area over recent years and further exacerbated by a lower catch limit based on the trend in biomass estimates. One effect of this variable spatial overlap is that tag recaptures have varied substantially between years; limited recaptures will lead to more uncertain biomass estimates and can lead to a reduction of catch limits.
Structuring of fishing in the area to ensure spatial overlap started with the 2023 season, with the requirement that each vessel participating in the exploratory fishery was to complete at least five research hauls outside the two main fished areas. Six tagged toothfish were released in 2023 on a seamount that was last fished in 2017 at which time a large catch came from that feature. The effect of structured fishing was greater in 2024, when fishing also occurred on seamounts 2, 9, and 10, spreading tagging to two seamounts that had not been fished since 2020 and 2021, respectively. We recommend that the structured fishing along with the delayed start of the season in 88.2H, as required by CM 41-10 (2022), be continued, to improve mark recapture data and to better index the biomass for the seamount complex.
While this report primarily summarizes the two years of structured fishing in the northern Amundsen Sea region, we encourage Members to continue ageing work and to make their age data available, and we recommend that the Secretariat engage with Members engaged in otolith ageing to determine how best to integrate age reading data into the CCAMLR database. These data are needed should an integrated stock assessment be developed for the region.