Oh, you're different from Iskierka indeed, in that way. That one came right out of the shell looking for a fight. She was just a tiny thing, barely bigger than a dog, and she was ready to take on a full-grown heavyweight over rights to eating a cow. I've seen many dragons in China and the Incan Empire who didn't care much for fighting at all, though, so I think it's mostly a matter of personality and breeding. Temeraire falls somewhere in the middle - a fighting scholar, with a fighting gentleman for a captain. They suit each other well.
We do have female captains, aye - all the Longwing dragons have them. They'll let men serve on their crews, but they'll only have lady officers in charge.