The Prince Rupert coat of arms is a shining example of why we have the Canadian Heraldic Authority (to prevent civic committees from creating and using devices such as this one). The symbolism is clear- the setting sun (Prince Rupert is in the westernmost part of the westernmost province of Canada), the salmon (fishing industry), the pine trees (lumber industry), the wheat (I think that's wheat- agriculture?), and the beaver (Canadian industriousness and perserverance). The cross may be to symbolize Christianity, or simply to separate the various charges. I've no idea what that diagonal line is- it's not slanted enough to be a bend sinister, and it appears to be a partition line only until it hits the wheat, which appears on either side of it.

The motto (as near as I can make out) reads, "With the net and pick, by rail and ship, we win our wealth", a detailed description of the city's industries.

Image taken from here.