Ehhhh, that would only be true if you finagle trauma into a very limited set of behaviors post trauma.

Fish do have an avoidance mechanism where they won’t revisit places that they’ve been startled or injured in

But they also lose that behavior over time as long as the events are reproduced. Which happens in mammals, including humans, too; just not as fast or as easy.

You gotta understand that most fresh water fish operate in smaller ranges, so if they held onto the trauma response too long, then their entire territory becomes locked off. So their brains run a more limited avoidance pattern than what we do. But they do have them

While it would b e possible to dick around with the semantics around what is and isn’t “trauma”, fish absolutely have fear responses and avoidance of locations after injury or stress. If you don’t want to call that trauma, fine, whatever. But it is a mechanism very similar to what mammals, birds, and even reptiles have.

It isn’t about intelligence at all. It’s about memory and risk aversion.