Which of these words is a collective noun for a group of otters?

They're vicious little things, it could've been a riot

I don’t really like these collective nouns for animals. They are used by literally nobody except trivia quiz compilers. Can you imagine an ornithologist referring to “a larger unkindness of ravens living on the west side of the mountain”, or a zoologist commenting, that “there were six new otter pups in the rump I was studying last spring”. They are nonsensical terms.