Nature News

With Whales at Record Numbers off the California Coast, Scientists Try to Help Ships Avoid Them

July 1, 2020
blue whale tail
A blue whale dives in front of a container ship in the Greater Farallones National Marine Sanctuary. (Photo by John Calambokidis, Cascadia Research Collective)

In September 2014, John Calambokidis was on a boat following a tagged blue whale in the Santa Barbara Channel when he and his colleagues saw a very large ship approaching. The whale had two tags on it, allowing Calambokidis, a senior research biologist and founding member of Cascadia Research Collective, to see exactly how deep it was, how it was angled, and how fast it was surfacing.

The ship, a 263-ton container ship called the Mokihana, approached the whale at about 11 knots. The whale, which had been resurfacing from a dive, drew closer. A collision, Calambokidis recalled, seemed inevitable. Then, about 100 meters from the ship, the whale stopped. It remained about 70 meters below the surface until the ship passed. Calambokidis and his research boat, which had been following the whale closely, sped out of the way themselves.

It was the closest documented encounter between a large commercial vessel and a blue whale, and, Calambokidis says, an anomaly because the whale avoided the boat. “What we discovered was that the reaction was only because it was deep and coming to the surface. It didn’t suggest that the whale was very aware or took any evasive action till the last second,” Calambokidis said. “Why would they think to react, given this is something new they are facing that hasn’t been a threat to them through their evolution?”

Collisions are one of the major human causes of mortality for large whales, along with entanglements in fishing gear. When blue, humpback and fin whales migrate along the West Coast during the summer, their paths often overlap with shipping activity, especially in shipping lanes leading to and from major ports like San Francisco, Oakland and Long Beach.

Between 1988 and 2012, there were at least 100 documented large whale ship strikes along the California coast. Research suggests that this number dramatically underrepresents the true death toll because many ship strikes go unobserved, and the carcasses of large whales often sink instead of washing up on the beach.

In 2017 researchers at Point Blue Conservation Science tried to come up with a more accurate estimate by modeling ship strikes. Point Blue Senior Marine Ecologist Cotton Rockwood used an encounter model, similar to models used by navies to estimate risks of ship collisions, to find mortality estimates. Basically, the model asks: if there are a certain number of ships moving in an area and there are a certain number of whales in that area based on their distribution, what is the probability that they would intersect and hit each other? Rockwood then showed how many whales could potentially be saved from strikes with different types of participation from the industry.

The modeling shows collision avoidance by whales under three scenarios: decreasing avoidance with increasing vessel speed, constant 55 percent avoidance, and no avoidance. (In one collision study, researchers found that in 55 percent of observations, the whale changed its behavior to avoid the ship.)

The model estimates that about 80 large whales, 18 of them blue whales, are killed by vessel collisions in the California-Oregon-Washington area each year. For all three large species (blue, humpback and fin), mortality rates were significantly greater than what scientists call potential biological removal, or the number of whales that can be taken out of the population by people without affecting overall population stability.

“This assists us by giving us a clearer number of how big the problem is, essentially,” said Mary Jane Schramm, media and outreach specialist for the NOAA Greater Farallones National Marine Sanctuary. “It clarifies the problem in scope — the geographic as well as the number scope.”

For all three species the modeled mortality was unsurprisingly greatest along central and southern California, with large numbers of deaths occurring along the shipping routes between the port of Long Beach, Los Angeles, and the San Francisco Bay Area.

So on June 13, 2020, when biologists spotted at least 47 blue whales in the span of an hour from a vantage point on the Farallon Islands, off the coast of San Francisco, they knew the whales were at risk. About a dozen heavy ships – containers, tankers and bulk products ships – pass through the Farallones and Cordell Bank marine sanctuaries daily, en route to the San Francisco Bay, according to John Berge, vice president of the Pacific Merchant Shipping Association in the Bay Area and a member of the Greater Farallones National Marine Sanctuary Advisory Council.

Berge said that ship traffic decreased about 7 percent in the sanctuaries from January to April 2019 to January-April 2020, from 1,126 ships to 1,045, and that he didn’t have numbers for May and June but estimated a similar slight decrease.

In June the two national marine sanctuaries, Cordell Bank and Greater Farallones, sent out alerts advising all vessel operators to avoid the blue whales that had moved into the sanctuaries to feed. The U.S. Coast Guard also notified mariners to reduce and maintain slow speeds (10 knots in critical whale areas) and maximize possible distance to avoid collisions. Two iPhone mobile apps also show estimates of where individuals whales are, based on whale observations from scientists and amateur whale watchers alike.

Point Blue researchers on the Farallones log observations for about an hour every day – the species they see, how many there are, how far from the island, and what angle relative to the island — as part of a daily count of whales since 1987. The information is added to the app and harvested by Point Blue’s server about every two hours, so people who have signed up for the alert system get information about sightings in near real time.

“If the numbers are higher than usual, then agencies like NOAA may take additional actions,” said Jaime Jahncke, who directs the California Current program at Point Blue. “In this case because our observations showed about 47 whales south of the island, closer to where the shipping lanes are located, NOAA decided to put a notice out to mariners in the area asking them to please slow down when transiting the sanctuaries and traveling into the Bay.”

Another advantage of the record of daily sightings data is that Point Blue now has over 30 years of data. Based on their work, Jahncke said, there are now more whales than there were in the 1990s, and whales are also arriving earlier than they once did, likely because of shifting ocean patterns attributed to climate change. Whales used to be common off the Farallones in late summer and fall, but now they arrive early in the spring and stay for a longer period of time. In the case of blue and humpback whales, this means a 100 to 150-day earlier arrival than in the 1990s. “As we collect this data, we can continue to improve on our analyses so we can figure out ways to separate whales from human activities and decrease the risk of ship strikes, entanglements, and other threats they face from us,” Jahncke said.

About the Author

Mukta Patil is a freelance science writer based in the Bay Area. She loves the California poppy, Muir Woods, and Pacifica.