The number one piece of advice for ship captains looking to reduce the risk of whale collisions? Slow down.

That's according to a new industry handbook, the Mariner's Guide to Whales, Dolphins and Porpoises of Western Canada, which aims to reduce the impact of B.C.'s shipping industry on marine wildlife.

Caitlin Birdsall, program coordinator at the Vancouver Aquarium's Coastal Ocean Research Institute, says the handbook provides information and practical advice for ships to help avoid collisions in areas with large cetacean populations.

Many of the areas the handbook identifies as having high whale population densities are also busy shipping routes, such as the Strait of Georgia, near Vancouver, and the Hecate Strait, near Prince Rupert.

One of the biggest ways ships can reduce collision risk, Birdsall said, is to slow down in those high-density areas.

"Research from other parts of the world has shown that when vessels reduce their speed to 10 knots or lower ... it can great reduce the chances of ship strikes happening," she said.

B.C. whale population density

A chart from the handbook shows relative cetacean population density along the B.C. coast. (B.C. Cetacean Sightings Network)

Large ships may not even notice strikes

When ships strike whales near major ports, it often becomes a high-profile news story. But Birdsall said it's hard to know just how big a problem whale collisions are in the industry.

She said many strike reports come from smaller vessels, but that's not necessarily because they're more likely to hit whales — they're just more likely to notice.

"We don't have a lot of data about known strikes with large vessels because often they don't even know it has happened," she said.

"They're on such a big boat [that] they can't see the front of the bow or they can't feel the impact of that strike because they're so much larger than the animal."

Birdsall said captains of vessels of all sizes can help scientific efforts by reporting any whale sightings to the B.C. Cetacean Sightings Network.

The handbook recommends posting extra watch staff while travelling through high-density whale areas to help reduce the risk of a collision.

Fin whale close blood

Whales struck by ships often become big news, such as a recent case of a dead fin whale in Vancouver. (Belle Puri/CBC)

Industry keen to reduce impacts

In addition to collisions, the handbook also discusses how things like regular maintenance and emerging propeller design technology benefits whales by reducing noise, which affects their ability to hunt and communicate.

The Port of Vancouver recently implemented voluntary noise level standards that can result in big savings for complying vessels.

The new handbook is the result of collaboration between the Vancouver Aquarium, the Port of Vancouver and the Port of Prince Rupert.

Birdsall said the project convinced her that the shipping industry is genuinely interested in reducing its negative impacts on marine wildlife.

"They're really open to finding ways to reduce their impact, and I think that's really encouraging," she said.

The handbook can be found online on the B.C. Cetacean Sightings Network's website.