You wouldn't have posted this if he didn't have a straight flush.
Saying that, looking over the hand again, fish play their hands extremely face up with their bet sizing. They min-raise because they think 'hey if I min-raise, it keeps him in the pot, he doesn't need to pay much to call, I don't want to scare him away, maybe he thinks I'm bluffing with this tiny bet size' not realising that to any half decent player, the min-raise from a fish is a sign of huge strength. The double min-raise just gives it away.
I take back the comments in my first post, I think you could actually fold this, but maybe I'm being results oriented