Basking sharks (Cetorhinus maximus) are one of the largest fish in the sea, second only to whale sharks. They can reach a maximum size of 45 feet (Miller and Lea 1972), and are distinguished from whale sharks by their pointy snouts, dark grey to brown color, and gill slits that nearly encircle their head. Like whale sharks, as well as all the largest rays and cetaceans, basking sharks are filter feeders foraging near the base of the food-web on krill and other zooplankton. Consequently they have no interest in divers, surfers or swimmers.
Basking sharks are found around the world but are seen mostly nearshore in temperate waters where currents act to concentrate prey. Off the West Coast they have most commonly been documented off Canada and Central California. In both locations up to the mid 1900’s basking sharks were targeted by fisheries or eradication programs that killed a large numbers of individuals. While historically animals were reported in the hundreds and thousands, more recently only a few individuals have been seen in any given year.
In response to the apparent decline in local populations, NOAA recently listed the basking shark as a “Species of Concern”. Some reasons for this listing are the apparent reduction in numbers, the lack of a recovery in population size despite around 50 years without being targeted and lack of information on very basic aspects of their biology. For example, we currently don’t know how old basking sharks are when they first reproduce, where they have their young, what the range of their movements are or the structure of their populations. Collecting this type of information will help us to understand how both the environment and human activities influence basking shark numbers as well as aid in the development of a recovery plan for basking sharks off the West Coast of North America.
This Wildlife Computers MK10-PAT, Fast-GPS tag is the type of satellite tag used in this study. The tag is attached just below the dorsal fin on the back of the shark. The leader extends away from the shark's body, allowing the tag to float along beside it. When the shark is swimming at the surface, the antenna should break the water's surface and communicate with satellites.
To begin to answer these questions NOAA Fisheries, Southwest Fisheries Science Center recently initiated a study on basking shark off the West Coast. One component of this study is to use satellite technology to track the movements of basking sharks and determine how oceanography influences where they go and what they do. The satellite tags will record temperature and depth throughout the track allowing us to look at habitat use. To determine the shark’s locations the tag will both link to GPS satellites when it is at the surface and record light levels which will allow us to estimate latitude and longitude.
NOAA scientists were expecting to tag basking sharks with collaborators off Canada where they have most commonly been seen in recent years. However, this year the forces of nature delivered unexpected numbers of basking sharks to our doorstep. On Sunday June 6th, 2010, a basking shark was tagged with a satellite tag off Pt. Loma. This is the first basking shark tagged in the Pacific Ocean.
We will update this website as tag information returns, so stay tuned!
How you can help!
If you see a basking shark while you are on the water and can call from your vessel, please call:
John Hyde at (760) 408-7726 or Heidi Dewar at (858) 546-7023.
If you wish to report a sighting after you have returned to land please provide the date, time and location of the sighting, as well as any comments to (858) 334-2884 or send an email to Heidi.Dewar@noaa.gov.
Any photos or video would also be appreciated and can be sent to:
NOAA Fisheries, SWFSC
8604 La Jolla Shore Dr.
La Jolla, CA 92037
Basking Sharks Tagged in June 2010
On Sunday, June 6th, 2010, eight miles offshore from San Diego, California, Dr. John Hyde, the supervisor of FRD's Molecular Genetics program, and Owyn Snodgrass, a member of the FRD Large Pelagics Program, successfully tagged a basking shark, the first time this has been done in the Pacific Ocean. The video shows the shark swimming slowly at the surface of the water. When the boat is maneuvered close enough, a Wildlife Computers MK10-PAT, Fast-GPS tag is affixed to the animal just below the dorsal fin using a long pole. **Note: This video has no sound.
Basking shark tagging video
Photo Credit: Gregory B. Skomal
Basking Shark Tag surfaced in February 2012
Basking sharks used to be abundant off the West Coast but numbers appear to have declined starting in the mid 1900's. In order to develop a recovery plan the U.S. has teamed up with Mexico and Canada to collect basic biological data on basking shark. One goal of that program is to place satellite tags on basking sharks to look at large scale movements. Three sharks have been tagged since 2010.On February 2nd, 2012, one of the satellite-based tracking devices outfitted last year resurfaced near Hawaii after eight months collecting data on the migration of the Basking shark. The San Diego Union Tribune published an article on February 13th that detailed the importance of such an event. The piece, entitled "Shark's journey a first for science,"featured an interview with Heidi Dewar of SWFSC. This is the first demonstration of a link between Basking Sharks in the Eastern and Central Pacific.