This article discusses the largely forgotten anti-whaling protests in Norway and Japan at the beginning of the twentieth century. It shows that fishing communities around the world protested almost simultaneously against the introduction of Norwegian-style industrial whaling, even though the protesting fishermen did not compete for the same marine resources as the whalers. Analysing Norwegian and Japanese fishermen’s knowledge reveals that whales played a crucial part in pre-industrial coastal fishing, as they were partly responsible for bringing fish closer to the shore. The article argues that fishing communities around the world had developed ‘coeval moral ecologies’, believing that the killing and flensing of whales caused environmental pollution, hurting coastal flora and fauna, and thus ultimately diminishing the coastal ecosystem on which the fishing communities depended. Fisheries scientists, politicians, and whalers have, however, downplayed this fishermen’s knowledge by presenting allegedly unbiased scientific data that did not indicate a relationship between whaling and fishing.