The coast of British Columbia is home to productive waters, astonishing marine biodiversity, and a booming shipping industry. All of this adds up to a very busy ocean! On any given day, trawlers, ecotourism boats, recreational vessels, large tankers, and cruise ships can be seen traveling along our coast. Unfortunately, this marine traffic exposes cetaceans to underwater noise and vessel disturbance, and increases their chances of fatal injury due to ship strikes.
In order to reduce the risk of cetacean-vessel collisions, the Vancouver Aquarium’s BC Cetacean Sightings Network embarked on a collaborative project with the Port of Vancouver and Fisheries and Oceans Canada to release the Mariner’s Guide to Whales, Dolphins, and Porpoises of Western Canada. This guide aims to improve environmental awareness in the marine transport industry by alerting mariners to areas with a high density of cetaceans. It also provides a guide for identifying cetaceans and sea turtles commonly sighted off our coast; using the guide, mariners can report their sightings to The BC Cetacean Sightings Network. These sightings are used to create an estimate of abundance and distribution of these animals in BC. The Mariner’s Guide has used this data to create a map that highlights areas where mariners are more likely to encounter a cetacean, and therefore where greater vigilance and reduced speed are required.
Studies (like this one by Vanderlaan et al. 2007) have shown that large, fast-moving vessels are more likely to fatally injure a cetacean upon impact. Researchers studying North Atlantic Right Whales on the East Coast found that the chances of a lethal injury from a boat strike declines from approximately 80% at 15 knots to approximately 20% at 8.6 knots. These studies provide evidence that a decrease in cetacean mortality will occur when large vessels reduce their speed in high-density areas.
Some species of cetacean are more prone to vessel collision than others. Fin whales are the most commonly struck cetacean worldwide, and ship strikes are the greatest threat to Fin whales in BC waters. They tend to spend most of their time along the coastal shelf, which coincides with shipping lanes, and their low frequency calls can be masked by vessel noise. Humpback whales have the second highest vessel strike rate in BC due to their relative abundance and their tendency to feed on the surface of the water. Blue whales are often struck because they feed at the surface, have a slow, shallow dive response when oncoming vessels approach, and spend more time at the surface at night when ship visibility is impaired. Pacific white-sided dolphins and Dall’s porpoises are at risk for vessel collision because they will often approach ships to bow ride. Harbour porpoises tend to inhabit urban areas and their small size makes them hard to detect. The endangered North Pacific Right Whale is particularly susceptible to vessel collision. Right whales respond slowly to approaching vessels, swim at slow speeds, and tend to rest and forage at the surface of the water. Ship strikes are thought to be the primary threat to the to the recovery of the BC’s small Right Whale population, where the loss of even one individual is detrimental to the recovery of the species.
Even animals that are less susceptible to ship strikes can be negatively affected by ship traffic. Vessel disturbance has been shown to reduce foraging activity, decrease social behaviours, and disrupt communication in killer whales. Increased vessel disturbance would add further stress to this endangered population, which is already threatened by low Chinook salmon stocks.
As marine industry in BC continues to grow and the environmental pressures on marine mammals increases, there is an urgent need to mitigate the impacts of ship traffic. By educating and informing mariners, this guide will help to decrease the incidence of ship strikes and reduce vessel disturbance. The guide will also increase the number of sightings reported and improve sighting maps, which will help researchers to better understand and protect cetaceans in BC waters.
You can also read how the Port of Vancouver plans to protect cetaceans by reducing marine underwater noise here.