Endangered Population of Killer Whales May be Most Affected by Ship Speed

Ships may need to slow down, a new study suggests. Scientists have found that the speed of vessels operating near endangered killer whales is the most influential factor in how much noise from the boats reaches the whales.

The whale watching fleet has increased from fewer than 20 commercial boats in the 1980s to roughly 80 boats serving about 500,000 people a year. There's an estimated $70 million value to the economy of Washington and British Columbia from this industry.

In the past, NOAA Fisheries has identified vessel traffic and noise as one of three main threats to recovery of the endangered population of resident killer whales, which now numbers about 80 animals. Now, researchers have found a way to possible reduce this noise.

The researchers collected data on the distance to the whale from each vessel in the area to see how they contributed to noise exposure. They also compared the characteristics of boats in the area with sounds recorded by hydrophones to see what factors most influenced the noise reaching the whales. In the end, the researchers found that it largely has to do with speed.

"It definitely seems that speed is the most important predictor of the noise levels whales experience," said Juliana Houghton, lead author of the new study, in a news release.

Limiting vessel speed in the vicinity of killer whales could reduce noise exposure to the population. However, noise isn't the only factor determining how nearby vessels affecting whales, which means that limiting ship traffic may be important to helping with the recovery of the species.

The findings are published in the journal PLOS One.

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