Backgrounder

Stability information for the investigation (M15P0286) into the September 2015 capsizing and sinking of the fishing vessel Caledonian off the west coast of Vancouver Island, British Columbia

Occurrence

On 05 September 2015, the fishing vessel Caledonian, a large, 100-foot fishing vessel with four crew members on board, capsized and sank 20 nautical miles off the west coast of Vancouver Island, British Columbia. One crew member was rescued and the bodies of the remaining three crew members were recovered.

Fishing vessel stability – Key points

A fishing vessel that is stable returns upright after it has been heeled over by tilting forces acting on it. These forces include the wind and waves, the weight of the vessel and its equipment, as well as the weight of catch, fuel, gear, freshwater, and other items onboard, particularly if they are off-centre.

When one (or more) of these forces heels a fishing vessel over, the force that brings it back up is called buoyancy. The amount of buoyancy that a vessel has for bringing it back up depends a lot on its freeboard. Freeboard is the distance between the water and the vessel’s main deck. As a fishing vessel gets heavier, it floats lower in the water and freeboard is reduced. In general, vessels that have more freeboard are more stable.

Another thing that can affect a fishing vessel’s stability is its centre of gravity, or the combined centre of all the weights that are onboard the vessel, including the weight of the vessel itself. In general, vessels that have a lower centre of gravity are more stable. The centre of gravity can be raised when catch is lifted by the boom, or stowed on deck. This can also happen when modifications are made to the vessel that add weight up high, such as if these modifications are made above the deck level.

For the fishing vessel Caledonian, there were several factors that combined to reduce its stability, leading to its capsizing:

  Factor Effect
1 Weight creep – over about 39 years, the vessel’s weight increased by about 50 tons
  • reduced freeboard
2 Modifications - the original net drum was raised and a second net drum and trawl were added
  • reduced freeboard
  • centre of gravity raised
3 Operational practices – the way fuel and water were stowed meant that the vessel was trimmed by the stern (floated deeper at the back)
  • reduced freeboard (at the back of the vessel)
4 Operational practices – the way fish were loaded meant there was extra weight above the deck
  • reduced freeboard
  • centre of gravity raised
5 Water on deck – when water came on deck, the extra weight was trapped and could slosh around
  • increased tilting forces
  • reduced freeboard
  • centre of gravity raised
6 Lifting weights – fish were lifted off the deck with the boom
  • centre of gravity raised