Aspects of body size and gonadal histology in the Antarctic toothfish, Dissostichus mawsoni, from McMurdo Sound, Antarctica

Twenty-eight specimens of the large othenioid Dissostichus mawsoni were dissected alter capture on a set line near the southern limit of its range in McMurdo Sound, Antarctica. Total length (LT) averaged 127.3 cm (range 90-162 cm) and weight(W) was 26.7 kg (range 10.4-60.3 kg). The length-weight relationship was W = 3.34 x 10(-5) L-T(2.85) (n = 28, r(2) = 0.96) Subcutaneous lipid thickness averaged 2.6 mm and showed no difference due to sex, but a significant weak relationship to W and LT Hepatosomatic index (IH) was 1.6% for females and 1.7% for males; gonadosomatic index (IG) was 0.9% for females and 0.2% for males. Although specimens were large and sexually mature, the histology indicated that the gonads of this November sample were in a resting stage. Testes lacked spermatids and spermatozoa. Oocytes were previtellogenic stage (91.2%) or in the first oocytes and empty follicles females in this sample had spawned previously. A summary of the life-cycle is also presented.