It is hard to believe that scientists need help finding one of the largest fish in the ocean. But so few basking sharks remain in the waters off California that researchers are hoping the general public can assist by reporting any sightings to scientists who are interested in electronically tagging and then tracking these animals to learn more about their behavior and distribution.
The basking shark was recently listed as a “Species of Concern” by NOAA’s National Marine Fisheries Service, a category indicating concerns scientists have about the populations future viability. It is estimated the number of basking sharks once numbered in the thousands off the coasts of the U.S. and Canada, before their numbers plummeted in the mid-1900s due to human exploitation. Today these sharks are rarely seen.
Basking sharks are found around the world but are seen mostly near shore in temperate waters where currents act to concentrate prey. Off the West Coast they have most commonly been documented off Canada and Central California. Similar to the larger whale sharks, basking sharks are filter feeders foraging on plankton at the base of the food web. Consequently they have no interest in divers, surfers or swimmers.
It’s all in the tagging
This spring, two basking sharks were tagged with satellite tracking devices, as well as one other last year. Eight miles offshore from San Diego, Dr. John Hyde, the supervisor of NOAA Fisheries’ Southwest Fisheries Science Center Molecular Genetics program, and Owyn Snodgrass, a member of the Center's Large Pelagics Program, successfully tagged these basking sharks. Last year’s taggings were the the first time this has been done in the Pacific Ocean.
Satellite technology is being used to track the movements of basking sharks and determine how oceanography influences where they go and what they do. The tags record temperature and depth throughout the track, allowing NOAA scientists a look at habitat use.
To determine the shark’s locations, the tag links to GPS satellites when at the surface and it records the amount a visible light, which providing estimates of latitude and longitude. The tags from last year showed that the sharks leave San Diego and move northwest to the Channel Islands and finally to Morro Bay where the tag dropped off. The temperature and depth show incredible diversity with dives to over 500 meters and the changes in habitat use are likely in line with the shifts in food distribution.
Learn more about the project or watch a video of the tagging effort.
How you can help!
If you see a basking shark while you are on the water and can call from your vessel, please call (760) 408-7726 or (619) 743-9004. If you wish to report a sighting after you have returned to land, please provide the date, time and location of the sighting at either (858) 334-2884 (Southern California) or (831) 771-4438 (Central California, north of Morro Bay). You can also email us at email@example.com. Photos or video are appreciated.
For more information see: