The only "Jonna the Whale" association I can think of is the whale who swallowed Jonah. Jonah was not the name of the whale.
Johanna- I would prn. it Jo-Hawn-ah. Jonna would be like JOHN-ah. Jonah would be JO-nah.
I am just very confused, but to answer your question none of these names makes me think of a fat lady....