Maybe a fish on the shirt. (Bass, Trout, Pike or Musky)
Maybe sillouhette of lure (use shape of lure from http://www.dynamiclures.com)
Maybe Fishing Rod (no flyrod). Baitcaster or spinning reel.
I would like it more of a modern feel rather than a classic feel like the old style fishing signs. (no old classic feel)
I like modern, sporty, techy, type design feel.
I would like to portray a modern, hip, sporty feel to the fishing shirt.