From UT San Diego: Shark's journey a first for science
An electronic ID tag from a rare shark spotted off the county’s coast in June has popped to the surface near Hawaii, providing local marine researchers with an unprecedented look into the long-distance movements of the second-largest known fish.
Basking sharks have almost disappeared from the West Coast, but biologists at the National Marine Fisheries Service in La Jolla found two last year and outfitted them with satellite-based tracking devices in hopes of learning more about where they roam. One tag fell off after several days but the other lasted eight months — enough to provide the first long-term track of a basking shark moving across the Pacific Ocean.
“It’s a big gold mine,” said Heidi Dewar at the Southwest Fisheries Science Center. “Now we know for sure that our animals can go to the central Pacific.”
The long-distance tag, which surfaced on Feb. 2, uploaded long streams of data about where the shark traveled, water temperatures it encountered and the animal’s depth as it traveled.
The basking shark, second only to the whale shark in size, has largely disappeared from West Coast waters. A research team from San Diego is part of an international effort to better understand the creatures and track their movements.
The basking shark, second only to the whale shark in size, has largely disappeared from West Coast waters. A research team from San Diego is part of an international effort to better understand the creatures and track their movements. — Greg Skomal
“We can look to see how the habitat use changes as it moves from coastal habitat to offshore habitat,” Dewar said. “That becomes important in the context of management and conservation.”
Agencies in Canada, Mexico and the United States are trying to safeguard basking sharks, which once gathered near the coastline by the hundreds or thousands. In recent years, however, sightings have dwindled and biologists have speculated that as few as 300 swim along the West Coast.
While basking sharks have gaping mouths and can grow up to 40 feet, they aren’t a threat to people. They are filter feeders that consume large volumes of zooplankton. As their name implies, basking sharks spend a lot of time at the surface — at least when they are near the coast — and are notably docile when researchers approach.
Still, they once were targeted for eradication off Canada because they got snagged in fishing nets. The population may also suffer because the sharks don’t appear to be frightened by oncoming boats enough to get out of the way.
At the Pelagic Shark Research Foundation in Santa Cruz, executive director Sean Van Sommeran said he started receiving data from a basking shark tagged near Pacific Grove in August. The tag -- part of a project with NOAA, Stanford University and the foundation -- released from the shark hundreds of miles off Baja California, providing researchers with a treasure trove of travel information.
"I would characterize it as an avalanche of data," said Van Sommeran said Monday.
He compared the current advancements in basking shark research to similar breakthroughs for white sharks about a decade ago. Both species were once thought to stay primarily along the coast.
"They are moving farther and wider than was previously understood or believed," Van Sommeran said.
Dewar said new data about the basking shark's trip to Hawaii is both exciting and daunting, because it means that effective protections must account for international waters. That’s difficult because basking shark fins can fetch tens of thousands of dollars for an Asian soup that some consider a delicacy.
Dewar and her colleagues ramped up an outreach campaign about basking sharks last summer in hopes of getting real-time tips from divers, boaters and others who see them. The researchers have two more satellite tags they are hoping to deploy in late spring, when basking sharks tend to be spotted in local waters.
This time, Dewar plans to program the tags to stay attached longer than eight months in hopes of determining what basking sharks do after they reach the central Pacific. Do they keep going to Indonesia? Do they turn around? Do they roam there for years?
The federal research group’s website is http://swfsc.noaa.gov/baskingshark/. Sightings can be reported to (858) 334-2884 or email@example.com. For each encounter, scientists want to know the date and time, latitude and longitude (or at least the general location), the animal’s estimated length, the number of basking sharks in the area, and other details such as water temperature. They also want photos and videos.