We're gonna need a bigger boat
Gentle giants return to Channel Islands National Marine Sanctuary
By Pike Spector
Spring is notoriously windy along the coast of California. Strong northwest winds can cause hazardous sea states to crop up out of nowhere, especially in the Santa Barbara Channel. But as dawn broke on a crisp April morning, the first rays of light revealed a glassy, calm channel. Not so much as a ripple disturbed the surface. These were perfect conditions for spotting one of the most elusive visitors to the channel’s waters: basking sharks.
Most mariners aren’t actively looking for giant, fearsome-looking marine creatures. But researchers from NOAA’s Channel Islands National Marine Sanctuary set out with – and accomplished – one goal: to put satellite tags on the gentle giants once seen in great numbers roaming the rich waters of the Santa Barbara Channel.
Prior to this, only four tags had been deployed on basking sharks in the eastern North Pacific and none had been deployed since 2011, despite many hours on the water. In recent years, basking shark sightings off of California have been rare, further complicating efforts to better understand these mysterious animals. With not one, but two, sharks tagged, this collaborative effort between NOAA scientists from the sanctuary and the Southwest Fisheries Science Center will bolster our understanding of these visitors to Channel Islands National Marine Sanctuary.
“The sanctuary is home to a number of really amazing pelagic species and most people don’t realize massive basking sharks are right in their backyard,” says Ryan Freedman, a researcher at Channel Islands National Marine Sanctuary. “However, as more people see these cool fish, we need to ensure the public views them responsibly. The first shark we saw had obvious boat propeller scars on its dorsal fin. It is critical for our communities to protect and support this species of concern.”
Basking sharks, Cetorhinus maximus, are often mistaken for white sharks due to their large size and similar body coloration. Despite their appearance, these sharks are often shy and skittish, and typically avoid interacting with mariners. Basking sharks are the second largest sharks in the world, measuring up to 30 feet as adults, about as long as a school bus. Like whale sharks and unlike white sharks, these gentle giants filter feed on dense clumps of copepods, tiny crustaceans about the size of a grain of rice. Basking sharks tend to aggregate where oceanographic conditions act to concentrate their zooplankton prey, and are seen seasonally in temperate regions of both the North Atlantic and Pacific.
Despite their grand size and habit of swimming at the surface (hence the name “basking shark”), sightings of the population in the eastern Pacific declined in the latter half of the 20th century. In the mid-1900s, basking sharks were targeted in a number of fisheries in the eastern and western Pacific and were also killed in an eradication program in Canada to keep them from destroying fishing gear. Other individuals were killed as bycatch. While targeted fisheries in the Pacific ended decades ago, basking shark fins have a high value in Asian markets, creating an incentive for landing them and concern about continued fisheries mortality.
In 2009, NOAA scientists initiated a research program including a sightings database and an opportunistic tagging program to collect data on movement, behavior, and habitat use to support management. Scientists currently don’t understand how changes in environmental conditions may impact basking sharks, or even where the North Pacific population goes when they’re not along the West Coast. Do they swim to Japan? To Ecuador? Do they stay on the surface or do they forage at deeper depths? Our scientists are hoping to answer these questions, and more, with the help of satellite tags.
The pop-up satellite archival tags deployed by sanctuary personnel will remain secured to the sharks for up to 240 days, and will collect data on temperature, depth, and sunlight. After 240 days, they are programmed to release from the sharks, float to the surface, and transmit their data to satellites. Using the transmitted light data NOAA scientists can recreate the sharks’ movements. In addition, temperature and depth data provide insight into the sharks’ behavior and habitat use throughout the recording period.
“These data will help fill gaps in our understanding of basking sharks’ stock structure, their overlap with fisheries, and how oceanography influences the species’ distribution. All of this information is vital for the continued management and conservation of these poorly understood sharks,“ says Dr. Heidi Dewar of NOAA's Southwest Fisheries Science Center.
During the tagging event, Freedman and his team were also able to get two genetics samples. While collecting genetic material often requires a biopsy, DNA can be extracted from the shark’s mucus, a slimy coating on the surface of their skin. Until now, studies of basking shark genetics have excluded the eastern North Pacific because of a lack of samples. As with the tagging effort, genetic studies will provide valuable insight into stock structure both within the North Pacific and globally, and can also be used forensically to identify fins in the market.
Because of their elusive nature and the challenge of getting access to sharks for research, the only way this program works is by building a network across NOAA agencies and by working with the public. With these efforts, NOAA scientists are one step closer to unraveling the mysteries surrounding these charismatic creatures.
How you can help
Always use appropriate ocean etiquette when encountering marine life. If you see a basking shark, slow down to avoid hitting them with your vessel. They are easily injured and are susceptible to vessel collisions.
In areas with basking sharks:
- Slow down to six knots and avoid sudden changes in direction or speed.
- If you’re within 300 feet of a basking shark, switch your engine to neutral.
- Swim in small groups and do not closely approach basking sharks.
If you see a basking shark, please provide the date, time, and location of the sighting, as well as any comments, to 858-546-7023 or email firstname.lastname@example.org. Any photos or video would also be appreciated.
The mission of the Southwest Fisheries Science Center is to generate the scientific information necessary for the conservation and management of the region’s living marine resources.
Through research, education, outreach, and marine resource protection, NOAA's Channel Islands National Marine Sanctuary helps protected species and their marine habitats.
Pike Spector is a California Sea Grant State Fellow with Channel Islands National Marine Sanctuary.