Results of study of the oogenesis characteristics of Antarctic toothfish (Dissostichus mawsoni Norman 1937) (Nototheniidae) from Subareas 88.1 and 88.2 (Ross Sea)

The results of the histological analysis of the Antarctic toothfish (Dissostichus mawsoni) reproductive system, caught in December-March, 2004-2005 by the longliner VOLNA in subareas 88.1 and 88.2 in the Ross Sea are presented. The morphological parameters, indices of gonads have been described. The histological criteria of the assessment of the ovary maturity stages and cytological parameters of oocytes and type of the toothfish oogenesis have been determined. Under the maturing of toothfish ovaries from the stages II to IV show a slow increase in oocyte diameter. It was shown that for Antarctic toothfish during the fishing period the individuals with gonads of the III late stage of maturity were dominated. Their ovaries contained three size groups of oocytes: cytoplasmic group and two groups of vitellogenous oocytes. The type of the toothfish oogenesis has been defined as intermitted. The large oocytes of the nearest spawning season with average diameter 1000 - 1200?10-6 m have composed 5.4% of total cell number. The oocytes in the ovaries of analyzed fish did not reach the maximum size; consequently Antarctic toothfish was not matured for spawning in the Ross Sea during the investigation period.