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New data could help reduce collisions between whales and commercial ships in Southern California coastal waters

Study to help inform routing of ships in busy coastal waters

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Blue whales are threatened by collisions with commercial ships. Photo courtesy NOAA.

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Pinpointing whale densities helped researchers develop a map of shipping routes that could reduce the number of collisions.

By Summit Voice

SUMMIT COUNTY —After tracking whales for seven years off the coast of Southern California, scientists have assessed the risk of deadly collisions with commercial ship traffic. By predicting the density of endangered humpback, fin and blue whales in different areas, the study may help identify shipping routes the reduce those risks.

Based on their analysis, the scientists estimated that the number of the number of blue whales likely killed by ships exceeds levels established by the Marine Mammal Protection Act to ensure sustainable populations.

The study, published this week in the scientific journal Conservation Biology, merged observed whale sightings with oceanographic conditions to identify the habitat preferred by the different whale species. Scientists from NOAA Fisheries, the Marine Mammal Commission and Cascadia Research Collective collaborated on the project.

“We know several endangered species of whales occur in the waters off southern California,” said Jessica Redfern, a NOAA Fisheries marine mammal biologist and lead author of the paper. “What we didn’t know, and what this study helps provide, is an understanding of the areas with the highest numbers of whales.”

Knowing where whales are more likely to be found in the ocean environment is vitally important to reduce human impacts. Although this information could be used to assess any number of human impacts, the study specifically looked at current and alternative shipping routes to and from the Ports of Los Angeles and Long Beach and the risk to humpback, fin and blue whales from ship strikes.

Researchers selected four routes to study; the shipping route in the Santa Barbara Channel, which is the current shipping route; a Central route south of the northern Channel Islands; a Central Fan route, or just the eastern part of the Central route; and a Southern route, a course south of the Central route and constrained by the protected areas around Santa Barbara, Santa Catalina, and San Nicolas Islands. (See Figure 1)

By overlaying the routes with the predicted whale densities, researchers found the route with the lowest risk for humpback whales (Southern route) had the highest risk for fin whales and vice versa. However, risk may be ameliorated for both species in one of the Central routes. Blue whales, however, were at approximately equal risk in all routes considered because of their more even distribution throughout the study area.

“The Southern California Bight is an incredibly complex system with a diverse set of users, including the military, shipping industry and fishing industry. All users have specific needs and their input is necessary to plan the best and safest uses of these waters,” said Redfern, “This paper helps to incorporate whale habitat use in the planning process so that their needs can be considered as well.”

To learn more about this project or similar activities at the Southwest Fisheries Science Center, please visit the Ecosystem Studies Program website or contact Jessica Redfern.

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