(CNN) More than 120 pregnant whales were killed during Japan's annual hunt last summer, a report has revealed, prompting outrage among conservationists.

Figures show that 128 of the 333 minke whales caught during the 12-week expedition in the Southern Ocean were female. 122 of them were pregnant.

The figures were published in a technical report submitted to the International Whaling Commission and prepared by representatives of the Institute of Cetacean Research, an agency linked to Japan's fisheries ministry.

Conservationists greeted the report's findings with fury, calling the statistics "shocking" and condemning the slaughter as "abhorrent."

"It is further demonstration, if needed, of the truly gruesome and unnecessary nature of whaling operations, especially when non-lethal surveys have been shown to be sufficient for scientific needs," Alexia Wellbelove, Senior Program Manager at Humane Society International, said in a statement

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