Catadromy is the act of fresh water fish going to saltwater to spawn. They behave in the opposite way of almost every other species of fish. The opposite of catadromy is anadromy. Think salmon. They spend their lives in the ocean and return to fresh water to spawn.
Catadromous fish are like me. I almost never do what is expected. I do the opposite of what people think I should be doing, based on who they think I am. What can I say? So far, it seems to be working.