A company called Dizzy Pig makes some great seasonings. I use their Raging River or Shakin’ the Tree on fish all the time. Here’s the website: http://www.dizzypigbbq.com/
They are popular in the BBQ community as they also make rubs for ribs, brisket, etc.
I’m also a huge fan of Prudhomme’s Blackened Redfish Magic.