New data from Japanese catches in Antarctic seasons 1971–72 and 1972–73 are used to calculate biological parameters. Determinations are: fetal sex ratio (52.0% females); sex ratio in catch (54.1% females); [Formula: see text], males (27.9 ft), females (29.5 ft); age at asymptotic body length, males (18–20 yr), females (20–22 yr); male sexual maturity at testis weight (0.4 kg); length at beginning of sexual maturity, males (21 ft), females (24 ft) and at 50% sexually mature, males (23.6 ft), females (26.2 ft); age at sexual maturity, females (6 yr); apparent pregnancy rate (89.5%); annual ovulation rate (0.866); litter size (1.007); natural mortality coefficient of sexually mature sample (0.127) and of sexually immature sample (0.213); age at recruitment (6 yr); and rate of recruitment in virgin population (0.119).