I am a mac user with a canon camera. When I download from memory card direct to LR6 all photos are also stored on Image browser so I have duplicates of everything so storage compromised. Any solutions please?
Exactly what are you referring to by "Image browser"? Can you show us a screen capture?
You need to ensure that you only download in Lightroom. Macs by default open up the built-in Photos app. Don't download your images there too! See here for instructions on how to stop your Mac from opening Photos or Image Capture upon connecting a camera or card reader: How to stop Photos from auto-launching upon connecting an imaging device to your Mac