Channel 12 is the primary traffic channel for Halifax harbour; it's monitored by the coast guard VTS (vessel traffic services) who identifies on the radio as "Halifax traffic" - they keep a watch on ships in the harbour and give out harbour traffic information to ships, updates on other ships' locations, etc.
Channel 14 is also used by VTS for the outer approaches to the harbour, but depending on your location you may not hear it as often since the ships that they are communicating with are farther out.
This brings up a long standing question of mine.... Can you nowadays hear navy ships talking to each other? I mean tactical and liaison type comms not involving the public. When I was in the navy in the 70's we used the milair band extensively... 225-400 ... on AM ... just like military aircraft. As far as I know it was all in the clear as far as the transmissions were concerned but we used code words, though I guess any half decent scanner listener would figure it out in no time.