They are some of the largest animals on Earth, and it would seem difficult not to spot them.

But the greatest threat to the whales that ply the Pacific Ocean is the increasing vessel traffic that traverses what has become a marine superhighway.

A vessel strike is the most likely suspect in the death last December of an endangered killer whale found off the Sunshine Coast, north of Vancouver.

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Now vessel operators have a new tool that could help them avoid whale collisions off the West Coast.

Scientists at the U.S. National Oceanic and Atmospheric Administration have developed a program to predict where whales will be, giving vessel operators a greater chance to avoid collision.

"By the time you see a whale, it's almost too late; and it's probably the whale you don't see, that's just below the surface, that's likely to get hit," said Helen Bailey, WhaleWatch project leader at the University of Maryland Center for Environmental Science.

Using decades of satellite-tracking data gathered by researchers at the University of Oregon, reported sightings, data on ocean conditions such as sea surface temperature, food availability, winds, current and myriad other research, the WhaleWatch model predicts where the whales will be more precisely than ever before.

"When we know that's a hot spot, maybe then that's the time for some of these voluntary measures to help to reduce that risk," Ms. Bailey said.

For now, WhaleWatch focuses exclusively on blue whales, which rarely venture as far north as Canadian waters, but the aim is to add other species.

"We definitely would love to do it," said Elliott Hazen, a research ecologist at NOAA Southwest Fisheries Science Center.

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"We simply did not have the tagging data of sufficient numbers, at this point, to include [other species] in the model. That being said, it's on our to-do list and something we really want to do is to have a more complete analysis of multiple species."

Fin whales, humpback whales and grey whales are among their priorities but funding uncertainties mean they have no timeline for the additions.

While ship strikes are tracked and statistics are publicly released regularly in the United States, numbers are difficult to come by in Canada.

A DFO review last year found vessel collisions cause mortality for blue, fin and humpback whales off the B.C. coast, but didn't provide statistics.

What numbers there are, it suggested, likely underestimate the problem.

"In many cases, ship strikes are undetected by ship operators, and whale carcasses sink before drifting into coastal waters where they might be reported incidentally by coastal mariners. As a result, statistics based on direct estimates of wounds, or recovery or sightings of whale carcasses, underrepresent the true frequency of ship strikes," said the report from the National Marine Mammal peer committee review.

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In 2015, a dead fin whale arrived in Vancouver draped over the bow of a cruise ship. Similar gruesome sights unfolded on the city's waterfront in 2009 and 1999.

Approval of Kinder Morgan's TransMountain pipeline expansion into Metro Vancouver, and the estimated 350 additional tankers it will bring to port annually, has heightened concerns.

But it's not just tanker traffic.

About 3,160 vessels dock at the Port of Vancouver each year, an average of about nine per day. By 2026, the port conservatively predicts that will increase to 12 ships daily, or more than 4,200 a year.

Earlier this year, the Vancouver Aquarium's Coastal Ocean Research Institute, in conjunction with the Vancouver Fraser Port Authority and the Prince Rupert Port Authority, released a mariner's guide to try to mitigate ship strikes. The guide includes static maps of high-density areas for whales, dolphins, porpoises and sea turtles.

Last year, the University of Victoria launched an offshore-traffic-monitoring system using remote undersea gliders in an effort to do the same.

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But WhaleWatch is unique in trying to predict in real time where whales will be.

NOAA is in talks with the developers of a mobile WhaleAlert app to add their predictive model to their program. WhaleAlert currently tracks whale sightings off both coasts in Canada and the United States.

Industry has been very proactive in developing tools and voluntary measures to minimize its impact on whales, said Sonia Simard, director of legislative and environmental affairs for the Canadian Shipping Federation.

Real-time information on whale distribution can be an additional tool to ensure sustainable and efficient maritime transportation.

"Building awareness on how ships and marine mammals can safely co-exist is essential not only from a conservation perspective, but also to support the growth of sustainable maritime transportation throughout Canadian waters," Ms. Simard said in an e-mail.