If you would like your FishingMobile data erased then you need to:

1. Log into the website if you are not already logged in
2. Click on your username in the header
3. Click the "Edit" tab
4. Click the "Delete account" sub-tab
5. Click the "Delete" checkbox to confirm you want to delete your account
6. Click the "Save" button

If you get an error about missing profile data, you'll need to fill that (with nonsense if you like) in before doing the delete. This is a quirk of the system.