By Geoffrey Mohan, Los Angeles Times

Blue whales cluster for long periods of time in the busy Pacific Ocean shipping lanes off the California coast, raising concern about collisions between vessels and the endangered marine mammals, a new study has found.

Researchers used satellites to track 171 tagged blue whales over 15 years to produce the most detailed maps of the feeding areas of the marine mammals, which are protected from hunting under international regulations and are listed as endangered under the U.S. Endangered Species Act. The study was published this week in the online journal Plos One.

“It’s an unhappy coincidence,” said lead author Ladd Irvine, a marine mammal ecologist at Oregon State University. “The blue whales need to find the densest food supply. There’s a limited number of those dense places, and it seems as though two of the main regular spots are crossed by the shipping lanes.”

The biggest overlap between the whales and ships occurs between July and October near the western Channel Islands, off Santa Barbara, with somewhat smaller overlaps near the Gulf of the Farallones, near San Francisco, and farther north at the northern edge of Cape Mendocino, according to the study.

The study’s conclusions are at odds with some previous research, based on more rudimentary sightings of whales, that suggested that shifts in shipping lanes would not affect the whales because they are too widely dispersed. The new study found more dense concentrations and tracked them over longer periods of time, an average of two to three months. One whale remained tagged for nearly a year and a half.

“This is far and away the most detailed look that we’ve gotten on where these whales go, and the timing of when they’re present and when they move,” Irvine said.

“The nice thing about the satellite data is you get a longer-term snapshot that crosses over multiple years,” said Monica DeAngelis, a marine mammal biologist with the National Oceanic and Atmospheric Administration who has worked on previous efforts to protect whales from ship collisions.

“We knew that there were important habitat features in the ocean that we inferred these animals were homing in on, for feeding. But we were not sure of the extent of importance of these features,” DeAngelis said. “It gives us a lot more insight into what whales are doing.”

The largest animals on Earth, blue whales can grow to more than 100 feet in length and can weigh 150 tons. About 2,500 of an estimated worldwide population of 10,000 congregate in the waters off the West Coast.

In 2012, the International Maritime Organization agreed to divert southbound ships more than a mile away from Santa Cruz and Santa Rosa islands, off Santa Barbara, and elongated another lane in the Gulf of the Farallones, off San Francisco. Both changes came out of concern raised by increased blue whale sightings near areas where an upwelling in deep sea currents dishes up dense schools of krill, the primary food source of blue whales.

The process took years, and any new dialogue about further shifts is expected to take awhile, DeAngelis said.

The shipping industry, which has supported additional research on whale populations and behavior, has been somewhat wary of new regulation of shipping lanes.

“We’re looking to improve the science, and get the best handle we can on what the abundance, distribution, and behavior of these animals are so we can develop the best management strategy,” said T.L. Garrett, vice president of the Pacific Merchant Shipping Association, a trade group that represents ocean carriers. “But it needs to be recognized by all parties. We don’t have adequate data to make those kinds of management decisions yet.”

Garrett said he was not surprised by the report’s findings that whales and ships intersect at certain times, given what is known about the species’ wide patterns of movement. The association and the industry support efforts to develop real-time tracking of ships and whales, as is done for the right whale on the Atlantic Coast.

Garrett cautioned, however, that changes to shipping lanes could have unintended consequences for shipping and other marine life.

DeAngelis agreed. “You wouldn’t want to put something in place that would be beneficial to the blue whales but then might be detrimental to humpback whales or fin whales_or ocean users,” she said.

Researchers, regulators, shippers, and other interested parties are planning to meet in the fall to discuss the latest data, DeAngelis and Irvine said.

Photo via WikiCommons

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