Little Black Squares Next To Crew Members

Greetings!

Please excuse my ignorance, I'm new to this submarining thang, but when i was clicking to check out the crew status i noticed all of the crew member icons onboard my sub had small black squares next to them in the upper right corner. Are they mutineers? Cuz nobody wanted to do nothing and I sunk to the bottom and...nothing.

I hear that fatigue is symbolized by a red exclamation mark but I haven't seen one of them yet.

Thanks!
Jeff