Whale-ship collision hotspots: 93% have no protection measures

A global survey has found that shipping traffic overlaps with almost the entire range of all whale species but only 7% of the areas with the highest risk of whale-ship collisions have protection measures in place for the whales.

“Whale-ship collisions have typically only been studied at a local or regional level … and patterns of risk remain unknown for large areas,” says lead author Anna Nisi, a postdoctoral researcher at the University of Washington in the US. “Our study is an attempt to fill those knowledge gaps and understand the risk of ship strikes on a global level.”

The research, published in Science, focused on 4 species: blue, fin, humpback and sperm whales.

It found that the highest risk areas lay along the coasts of the Americas, southern Africa and parts of Asia.

The team found mandatory measures to reduce whale-ship collisions were very rare. These overlapped with just 0.54% of blue whale hotspots and 0.27% of humpback hotspots. Such measures had no overlap with any fin or sperm whale hotspots.

The findings are “timely” and “not surprising”, according to Vanessa Pirotta, a researcher at Sydney’s Macquarie University who was not involved in the study.

“Ship strike is a global problem and one that occurs here in Australia,” Pirotta tells Cosmos. She has co-authored papers which have assessed the impact of shipping on marine giants in Australian waters.

According to the non-profit organisation Friend of the Sea, 20,000 whales are struck by boats each year around the world. Many species are at increased risk of extinction because of such collisions, as well as other pressures such as overfishing by humans depleting the whales’ food sources.

Many other large marine animals, including basking sharks and whale sharks, are also at risk of ship collisions.

Pirotta says animals most at risk “are surface active like whales who come to the surface to breathe and feed, whale sharks, basking sharks.”

Robert Harcourt, also at Macquarie and not involved in the Science paper, says “it is a really excellent study”.

Harcourt says that previous research using depth trackers suggested that whale sharks were getting struck by ships more often than was previously thought.

“As container ships got bigger and bigger, even if they hit a blue whale, they don’t necessarily notice it. They sometimes come into port and they’ve got a fin whale or a blue whale draped over their bow, and they haven’t even known they’ve hit it because they’re so loud,” Harcourt explains.

The paper is an advance according to Harcourt because it uses some powerful models and the increased volume of data on whale movement and migration.

Harcourt says protection measures are surprisingly simple.

Shipping lanes could be temporarily closed according to the migration patterns of whales. “We do a lot of that for things like seismic surveys. We don’t allow seismic surveys in areas of high whale density,” Harcourt says.

“If you look at southern Victoria, the Otway Basin, they don’t allow seismic activities during the period when blue whales are feeding, which is about 3 months of the year.”

Another measure is to move shipping lanes away from “pinch points” such as the waters around the southern tip of Sri Lanka where there are large migrations of blue and sperm whales and a very dense shipping lane.

“If they were to move the shipping lanes just 10km further offshore, they would greatly reduce the likelihood of running into blue whales,” Harcourt explains.

“The other thing is to have ships slow down in areas where there are whales,” Harcourt adds. “There’s been a fairly recent, but very effective slowdown of ships going into the Salish Sea, which is the sea where Seattle and Vancouver are. They’ve reduced the speed, I think, down to below 12 knots.”

“It’s like when people cross train lines, they don’t have the perception of how fast that train is coming towards them, and that’s why people can get hit. Whales, presumably, are similar in terms of these big ships moving quite fast. So slowdowns in areas of high density is a really effective means of reducing the likelihood of impact.”

Harcourt says the paper lays out clear guidelines for how whale-ship collisions can be reduced while also not having a major economic impact.

“It’s really nice to have a large, collaborative group of people applying the latest modelling techniques to try and make a direct impact on conserving the world’s magnificent giants,” Harcourt says. “But we can’t rest on our laurels with that. There are many more species that are really vulnerable.”