When joining a crew or starting a journey, the full crew is listed. Also you can manually see who is in your crew from the menu.
However it is sometimes hard to notice when someone decides to leave, or when a new pirate has joined the crew.
I would love a simple on screen notification just to state:
"Pirate ... has joined/left your crew!"
That way you know who is around, and in the midst of a fight know who you can count on or if you're all alone.
It seems pretty helpful to myself to know if there is a new crew member that can help you out, and greet him/her by there name.