Followed one of these around as close as physically possible while holding a fish corpse. So close that the "feed fish" gray text was on screen, but never turned blue like when feeding a basilo. Also clicking the action buttons wouldn't feed it at 0 range. Woohoo looks like I'll have to force tame it or spawn a tamaed one. I love having to use console commands to make up for developer durpery. That's probably why they're in the game tbh.

Don't tranq it... the dex doesn't tell you that for some reason... drag fish to it and press the interact button to feed it.

If you tame one it’s useless so just kill it