The reefs, fortunately, are opaque, or reflect sonar. Kim Conway at Natural Resources Canada originally discovered them by multibeam mapping, so it was for resource purposes that the whole coast was mapped. The technology with mapping changes the resolution of the sonar. The first maps he presented to Fisheries and Oceans showed so many reefs, and they kept becoming updated. The managers, I believe, saw the new areas and wondered if they were reefs. That's how they were identified. We had spots on a map that we had to go and check with a remote-operated vehicle.
On June 8th, 2017. See this statement in context.