Easiest to identify is Atlantic Larch because it has no firefighting gear:
Atlantic Willow is a firefighting tug, with prominent water cannons:
Atlantic Oak is a firefighting tug with less prominent water cannons:
However Atlantic Oak has a sister tug named Atlantic Fir, based in Saint John:
This weekend Atlantic Willow was sent off to Liverpool to berth the ship Thorco Dolphin with wind turbine components and Atlantic Oak was sent to Shelburne for refit. When Atlantic Fir arrived to fill in I noted that something new had been added:
Up close then, there is now little doubt that one is seeing Atlantic Fir. but from a distance it still requires some experience to pick it out.