As a treat once in a great while? Maybe. If you must. But know a few things first.
There are a number of problems–some well established facts and others that are somewhat open to question–that make feeding fish regularly, whether raw or cooked, pretty gosh darn inadvisable. At least from the digging I’ve done. The problems stem both from what’s in fish and what’s not in fish.
So far, I count eight distinct ‘strikes’ against the idea of feeding fish, raw or cooked, to cats.