Fishy

From a comment on another post, this article about Barramundi.

The Barramundi species, like many other fish, are asexual, and undergoes a sex change during its life history, with all fish commencing life as males then undergoing a sex change to become females.

Well, well. More on Piscine Sequential Hermaphroditism in Hormones and Animal Social Behavior by Elizabeth Adkins-Regan.