I had a pirate fleet sitting off the coast of South Africa with 3 Galleons, a Cutter and a Brig. Funny thing is, they didn't actually attack anybody, as far as I could tell. I finally took them out, as they were kind of annoying, whenever my battle fleet sailed by and attempted to engage.
Edit: Your picture loaded after I typed my response. Yeah, so far, I haven't seen a pirate fleet that size. That's somewhat scary.