A bumper crop of krill along the West Coast this past summer lured whales into the paths of cargo ships. With five collision deaths confirmed, and many more suspected, the US Coast Guard is investigating ways to mitigate future losses of these rare mammals.
The first was a humpback whale with propeller gouges that washed up dead on the Farallon Islands, near the San Francisco Bay Area. Another was a female blue whale and fetus which washed ashore in Pescadero. A cargo ship hit a fin whale, beheading it and dragging the body into the Port of Oakland. Another fin whale with a damaged spine washed ashore in Ocean Beach.
California wasn’t the only state which experienced collision deaths. In Washington, a Bryde’s whale with a massive dorsal gouge was spotted floundering in the waters south of Puget Sound. It later died from its injuries.
A Bryde’s whale floundering south of Puget Sound after being hit by a ship. Photo by John Calambokidis, Cascadia Research.
Scientists believe that many more than five whales have been hit and killed, but since not all whale carcasses make it to the beach – blue whales, for instance, sink when they die – it’s impossible to get an accurate tally.
“What we do see is likely to be a fraction of the total number,” John Calambokidis, a scientist at Cascadia Research Collective, told Mercury News. “A lot go undocumented.”
Krill, swarms of shrimp-like crustaceans, is a major food source for many whale species. Because of the nutrient-rich upwellings produced by La Nina, the West Coast experienced krill explosion which attracted a lot more whales than usual to the region. Fishermen with 40 years’ experience in the area said that they’ve never seen anything like it, and whale watch outfits said it’s one of the best seasons they’ve ever had.
Unfortunately, in addition to krill and whales, the area is also attractive to boat traffic. Major shipping lanes run up and down the coast, and in many places coincide with krill blooms. While whales are big and seemingly indestructible, even the biggest blue whale, weighing more than 30 elephants, is no match for a 20,000-ton cargo ship.
“This problem is not going to go away,” Jackie Dragon, marine sanctuaries director for Pacific Environment, a San Francisco nonprofit, told Mercury News, “Ship traffic is predicted to double by 2050.”
One possible solution being investigated by the US Coast Guard is to impose speed limits on ships passing through areas where whales are known to be. Pacific Environment, a nonprofit organization, is asking the Coast Guard to lower the speed limit from 25 knots to 10 knots. However, this fix has elicited some skepticism as collisions have been documented even when ships are steaming as slowly as 5 knots.
Another idea is to move shipping lanes away from continental shelf drop-offs, where krill tend to congregate, as well as installing marine observers on board to spot potential collisions before they occur.
Last year, a rise in the number of whale deaths prompted a change to shipping lanes along the East Coast, mainly to protect the critically endangered North Atlantic right whale.