A whale of a study
Golden Gate humpbacks are tagged in research effort
Researchers have gathered first-of-its-kind data on humpback whales swimming in the shadow of the Golden Gate Bridge in a “thrilling” mission from Fort Baker.
Two federally permitted scientists from the Cascadia Research Collective tagged three humpback whales with suction cup recorders near the Golden Gate Bridge late last month, the first time data has been collected in such a way since an increase in humpback whale activity there in recent years.
The pair were keen on collecting data on the dives and behavior of the federally endangered whales in one of the busiest shipping channels on the West Coast as concern grows about ship strikes. Researchers John Calambokidis and James Fahlbusch set out from Fort Baker near Sausalito on July 23 to place the multi-sensor, time-depth recorder tags on the multi-ton whales to record diving behavior.
“We have to get pretty close to the whales, about 5 feet away,” said Calambokidis, senior research biologist with the Olympia, Washington-based Cascadia Research Collective. “You have to be sure to be in the right position. It’s all a bit nerve-wracking and thrilling.”
Dramatic video shows the pair maneuvering their 19-foot inflatable craft to a swiftly swimming humpback; then Fahlbusch deploys the data recorder with a pole. The suction tags transmitted the whales’ movements for the next two to six hours, then popped off as they are designed to do. All three tags were recovered later that day and the next day.
The data provided the first detailed information on diving and feeding habits of humpback whales inside the Golden Gate and San Francisco Bay, researchers said.
Some of the information showed the humpbacks are not diving deep. While they have the capacity to dive hundreds of feet, the Golden Gate humpbacks were only going down 100 feet or less as they chased anchovies. Water under the Golden Gate is as deep at 360 feet. The shallow dives are worrisome for researchers, who fear collisions with commercial and other craft that populate the area.
“It’s a major concern of ours,” said Mary Jane Schramm, spokeswoman for the Gulf of the Farallones National Marine Sanctuary, off Marin’s coast. “This is one of the busiest shipping lanes on the West Coast and to have wildlife in such close proximity, it’s a challenge.”
The U.S. Coast Guard has put out warnings to mariners to be on the lookout for the humpbacks, Schramm noted.
All the activity in the shipping lane may be desensitizing the whales to vessel movement, Calambokidis noted.
“They had little response to us, it was a little too easy,” said Calambokidis, who has conducted hundreds of similar tag operations along the West Coast. “They seem to be tuning out the noise around them. They seem less aware, which makes them vulnerable to ship strikes.”
The team also photoidentified several humpbacks, whose fluke patterns are individually unique. Cascadia has compiled a catalog of individual humpback whales for the eastern North Pacific Ocean.
This is the second year the humpbacks have been seen in larger than normal numbers in and around San Francisco Bay; on some days, more than a dozen can be seen. The humpbacks are migrating north and for some, the food-rich coastal waters off Marin are a final destination for the summer before they head south to Mexico and beyond for the winter. The working theory is that they are chasing food sources in the Golden Gate on high tides.
The whales can weigh as much 40 tons — 80,000 pounds — and newborns weigh about a ton. They measure up to 60 feet long, with females larger than males, and live about 50 years. Aside from anchovy and other small fish, the whales eat krill and plankton. They can eat up to 3,000 pounds of food per day. About 1,400 humpbacks feed along the California coast in the summer and fall.
In June 1970, humpbacks were designated as endangered under the Endangered Species Conservation Act after the species was hunted for decades. In 1973, the Endangered Species Act replaced the conservation act and continued to list humpbacks as endangered. But populations have rebounded.
“As they have come back we see an increase with human interaction and there have been entanglement (net) issues,” Calambokidis said. “We want to better understand their behaviors, especially in high-risk areas like San Francisco Bay.”