Whale watchers said Monday a whale was struck and killed Sunday near Alcatraz Island.
A naturalist aboard a whale watching boat witnessed the aftermath of the humpback whale strike.
It used to be whales would rarely travel deep into San Francisco Bay, but in the past three years, whale watching has become a common summer pastime. Naturalist Michael Pierson was aboard the Kitty Kat on Sunday and saw humpbacks feeding.
"They’re following those bait fish, so where ever those bait fish are, that’s where the whales are going to go," Pierson said of the whales.
The skipper of the whale watching boat warned a container ship, which maneuvered away from the big cetaceans.
But a few hours later, another ship struck and killed one of the humpbacks that was feeding in the middle of the bay.
Pierson believes the solution is for ships to slow to 10 knots or less when whales are seen in the bay.
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"About 45 percent of the shipping companies have voluntarily reduced that speed, which is great," Pierson said. "We want to see that, but we want that number to be much higher in order to protect these animals a little better."
Private boaters are encouraged to report whale sightings so that vessel traffic can alert ship captains. And smaller vessels need to keep their distance, at least 100 yards, from the animals.
On Sunday, Pierson saw a speed boat called Skater buzzing one of the humpbacks, doing donuts around the animal, even though people on the whale watching boat were yelling at them to stop.
"That can cause these animals to be stressed," Pierson said. "It can potentially scare them into the path of these oncoming vessels."
The speed limit for ships on the bay is 15 knots. Pierson said a report from the National Oceanographic and Atmospheric Administration recommends reducing speeds to 10 knots or less. He says that reduction has shown results of an 80 percent decrease in ship strikes.
