Spatial distribution and biology of Dissostichus mawsoni in Subarea 88.3, with notes on by-catch species

Antarctic toothfish (Dissostichus mawsoni) have been found in regions sampled throughout Subarea 88.3 at depths from 550–2000 m, with size distributions and catch rate (i.e. abundance), differing by area, and especially by depth. Size distributions along the slope were typically bimodal, comprised of both very small and adult fish. Toothfish catch rates were highest on the central portion of the slope (88.3 B). Consistent with observations from other areas, growth of D. mawsoni differed between sexes, with females being larger on average for a given length than males. Resulting von Bertalanffy growth curves were similar to those derived for Antarctic toothfish in the Ross Sea region. Based on histology, length at 50% maturity of female and male Antarctic toothfish was estimated to be 124.5 cm and 124.0 cm, respectively, with length at 95% maturity estimated to be 145.2 cm and 166.3 cm for females and males, respectively. Age at 50% maturity was estimated to be 13.06 years for females and 13.27 years for males. Age at 95% maturity was estimated 18.64 years for females and 21.16 years for males, however greater sampling is required to confirm these parameters. Further sample collection and examination of spatial patterns in the biology and stock structure of D. mawsoni and key bycatch species in Subarea 88.3 are recommended.