Basking shark

Basking Shark with photo credit

Basking sharks are one of the largest fish in the sea, second only to whale sharks, and they can reach a maximum size of 45 feet (Miller and Lea 1972). Despite its impressive size, little is known about the basking shark’s habitat, behavior, and migratory patterns in the Pacific Ocean.

Basking sharks are seen seasonally throughout temperate regions of the North Atlantic and Pacific, but have long been a rare sight in Southern California waters. In the mid 1900’s basking sharks were targeted by fisheries and eradication programs that killed a large numbers of individuals. While historically these animals were reported in the hundreds and thousands, more recently only a few individuals have been seen in any given year.  

Scientists currently do not understand how changes in environmental conditions may impact basking sharks, or even where North Pacific sharks go when not along the U.S. West Coast. In response, NOAA Fisheries launched a tagging and research program in 2010 to fill in these data gaps. In June 2010, Fisheries Resources Division staff successfully tagged a basking shark, the first time one had been tagged in the Pacific Ocean. In the years since, five additional tags have been placed (2011, 2012, 2019).

The pop-up satellite tags attached to the sharks collect data on temperature, depth, and light. After 240 days (or sooner depending on conditions), they pop off the animal, float to the surface, and transmit their data to satellites. NOAA scientists can then recreate the shark’s geographic movements using the light data. The temperature and depth data provides insight into the sharks’ behavior and habitat use throughout the recording period. 

While tagging the sharks, scientists also gather samples of their mucus, a slimy coating that contains their DNA. The genetic samples provide invaluable insight into the relationships between sharks within the North Pacific and the rest of the world, and can help determine if shark fins sold on the market come from basking sharks.

The elusive nature of the sharks requires a collaborative approach among scientists at NOAA and the public to learn more about them. Thanks to these efforts, NOAA scientists are one-step closer to learning more about these gentle giants.


How You Can Help If You See a Shark:

The skittish and slow-moving sharks are most easily sighted in calm waters where they crisscross the surface, sieving up copepods as they go. Scientists urge boaters to use caution around the animals to avoid collisions. If you see a basking shark please:
• Slow down to 6 knots and do not make any sudden changes in direction or speed
• Consider switching engines to neutral if closer than 100 yards
• Jet skis should stay 500 yards away
• Report sightings, date, time and location to: (858) 546-7023 or Basking.Shark@noaa.gov 

Sightings information will be added to the sightings database and will help identify opportunities for tagging. 


Read more 

We're gonna need a bigger boat: Gentle giants return to Channel Islands National Marine SanctuaryThe previous link is a link to Non-Federal government web site. Click to review NOAA Fisheries Disclaimer
Dewar, H. et al. (2018) Basking Shark (Cetorhinus maximus) Movements in the Eastern North Pacific Determined Using Satellite Telemetry. Front. Mar. Sci. 5:163. doi: 10.3389/fmars.2018.00163The previous link is a link to Non-Federal government web site. Click to review NOAA Fisheries Disclaimer