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    Preliminary review of Antarctic toothfish maturity in the Ross Sea

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    S.V. Piyanova and A.F. Petrov (Russia)

    Results of comparative histological analysis of gonads of female and male Antarctic toothfish Dissostichus mawsoni caught by Russian longliners in the Ross Ross Sea of the Pacific sector in 2004/2005 - 2006/2007 seasons are presented. Morphological indices of females and males, age, indices of gonads, fecundity, and condition by Fulton are described. The criteria of assessment of maturity stages of ovaries, cytological indices of oocytes, and the type of toothfish oogenesis are determined. It was established that in the period of fishing, females and males with gonads at maturity stage III were dominated. Ovaries contain two groups of oocytes of the period of trophoplasmatic growth and large oocytes of the nearest spawning season that comprise the smallest proportion of total sex cells. The individual absolute fecundity was 0.33 million eggs, relative fecundity –29 eggs per g. It is suggested that in the Ross Sea the termination of gonad maturity of toothfish takes place from March to April, and spawning takes place from June to August. By the histological data 7-40% females had prespawning ovaries condition, and diameter of their large oocytes was 1075 - 2331•10-6m in different years.