Japanese vessels killed 333 minke whales in Antarctic waters within the past six months—122 of which were pregnant females and 114 of them juveniles. This move has intensified longstanding debates over Japan’s justifications for whaling in the Southern Ocean in the name of science.

The legality of these hunts is complicated. Though a moratorium on commercial whaling was put in place in 1986, there is some wiggle room allowing countries to kill whales for the purpose of scientific research. A Japanese whaling program known as “JARPA II” used this gray area to kill roughly 1,000 whales every Antarctic summer season. (Norway still kills about this number of whales annually, while Iceland kills around 200).

But in 2014, the UN's International Court of Justice ruled that Japan had misrepresented JARPA-II as a scientific program, deeming it a commercial enterprise that violated the International Convention for the Regulation of Whaling.

Japan was ordered to cease all hunts in the Southern Ocean; instead Prime Minister Shinzō Abe rebranded the program “Newrep-A” and decreased the number of whales targeted to 333 a year. Japan’s Antarctic whale hunts resumed in 2015. Despite the reduction, there’s still ongoing confusion over whether the primary purpose of these hunts is scientific or commercial.

The global population of Antarctic minke whales is estimated to be around 500,000, so they are not threatened to the same extent as some cetacean species, such as blue whales or bowheads. For this reason, Japanese whalers argue that killing 333 per year is sustainable.

But the International Union for Conservation of Nature red list, which tracks endangered species, considers Antarctic minke whales to be “data deficient.” In other words, simply not enough is known about this species to judge if its numbers are in decline, or if lethal sampling is a sustainable practice.

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Minke whales can take about up to eight years to become sexually mature, and females normally are pregnant with a single calf for nearly a year, making it particularly disruptive to hunt them because the species invests so much energy and effort to raise calves to adulthood.

As much outrage as the killings have generated, Japan has stated its intent to continue these hunts until at least the mid-2020s. The next meeting of the International Whaling Commission, which takes place in September in Brazil, will provide an opportunity for the global anti-whaling community to pursue stronger oversight of the “Newrep-A” program.