This report characterises the Antarctic toothfish (Dissostichus mawsoni) fishery in CCAMLR Subarea 48.6 through the 2024/25 season, summarising catch and effort data, biological sampling, tagging results, age composition, and progress toward stock assessment. Since its inception in 1997, the fishery has evolved into a structured research program with four designated research blocks (486_2–486_5). In 2024, total catches included 460 tonnes of D. mawsoni and 5 tonnes of D. eleginoides, remaining within precautionary catch limits.
Over 8000 specimens are examined annually by scientific observers, with comprehensive data collected on length, weight, sex, maturity, and age. Standardised CPUE analyses show stable abundance indices across most blocks, with increased small fish presence in blocks 486_4 and 486_5 since 2020, suggesting possible recruitment. A length measurement bias for fish >110 cm was identified and corrected.
Age composition analysis based on otolith samples indicates that data from 2023–2024 are reliable, enabling estimation of von Bertalanffy growth parameters (L∞=170.2 cm for females, 167.0 cm for males) and maturity ogives (50% maturity at 124.9 cm for females and 118.7 cm for males). Earlier age data (pre-2023) will require re-reading. Age sample gaps remain for small (<110 cm) fish, which are critical for robust age–length keys.
Weight–length relationships were estimated separately for males and females, revealing sex-specific growth patterns (b=3.071 for females, b=3.024 for males), supporting the need for sex-disaggregated models in future assessments.
The tagging program has marked 27 741 D. mawsoni with 869 recaptures (3.1% recapture rate), providing insights into movement patterns and population structure. Electronic tagging and genetic analyses support a panmictic population within Subarea 48.6, with some long-distance westward movements following Weddell Sea Gyre circulation.
In the development of the stock assessment model, a preliminary integrated age-structured model using Casal2 is has been constructed. The model incorporates spatial structure based on designated research blocks (Areas-as-Fleets), and accounts for IUU fishing and operations outside the defined blocks. Sex-specific age–length keys are applied, and growth parameters are derived primarily from validated otolith data collected in 2023–2024. Particular attention is given to improving age composition coverage for small (<110 cm) and large (>180 cm) fish. Upcoming steps include sensitivity analyses and validation of catch data by research block and season to ensure robustness of model inputs and structure.
The fishery demonstrates successful integration of commercial operations with scientific research, generating comprehensive datasets suitable for formal stock assessment development. The research program has achieved its primary objectives while maintaining ecosystem integrity and provides a model for the development of assessments for CCAMLR data-limited fisheries.