Do I need to bring an interpreter to meet the immigration officer at the Canadian Consulate in Hong Kong?

You mean you can only speak Cantonese, not Mandarin. You don't need an interpreter.

But the most practical method is this. ..

Send an email to the consulate and ask, "Dear staff, I can only speak Cantonese, but I can't speak Mandarin. Do I need to bring an interpreter during the interview? Thank you for your time and cooperation. "

If you say yes, you need to bring it, and if you say no, you don't need to bring it.

E-mail address of Canadian Consulate: hkong@international.gc.ca