Changes in biological parameters of balaenopterid whales in the Antarctic, with special referece to southern minke whale

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Historical changes in biological parameters of the southern balaenopterid whales were comparatively examined by reviewing the reports and information as well as on the new analyses for the minke whale (Balaenoptera acutorostrata) in the Antarctic region during the 1920's and the 1982/83 season. Two types of density-dependent changes were identified; changes by catch intensity itself for the blue (B. musculus) and the fin (B. physalus) whales and changes by interspecific competition for the sei (B. borealis) and the minke whales. However, further considerations would be needed in the changes of the sei whale. Even though the recently proposed possible biases are considered, the following declining trend of age at sexual maturity for the minke whale is thought to be real; from 12-13 years in the mid-1940's to 7-8 years in the early 1970's and from 11-12 years in the late 1940's to 8 years in the mid-1970's, classified by the age of maturation which indicates cross sectional population (=year of catch). A change in pregnancy rate of the minke whale, from 0.55-0.59 in the 1940's to 0.78 in the 1970's was suggested by using a "balance equation".
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