| Left: A shortfin mako shark (Isurus oxyrinchus) equipped with a pop-off satellite archival tag (PAT tag) and a Smart Position and Temperature tag (SPOT tag). Right: A 3-D bathymetric visualization of the track made by a tagged mako shark in the waters of the Southern California Bight. Click the image to watch full animation video. |
Recent advances in satellite tracking technology allow scientists to essentially follow large pelagic fish on their ocean journeys without getting wet. NOAA Fisheries has been collaborating with the Tagging of Pelagic Predators (TOPP) program and Mexican colleagues at the Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE) to deploy satellite tags on blue (Prionace glauca), shortfin mako (Isurus oxyrinchus) and common thresher sharks (Alopias vulpinus) in the California Current. The U.S. has also teamed up with Mexico and Canada to tag basking sharks (Cetorhinus maximus) off the west coast of North America. The goals of these projects are to document and compare the movements and behaviors of these species and to link these data to physical and biological oceanography. This approach will allow us to both characterize the habitats sharks most frequently utilize or prefer and subsequently to better understand how populations might shift in response to changes in environmental conditions. This type of information is critical for fisheries management, especially in the face of climate change. Although we tag the shark with conventional tags, there are two kinds of satellite tags that are commonly used to study the movements of sharks:
Pop-off Satellite Archival Tag (PSAT or PAT tag)
PSAT tags are attached to the fish’s back where they record data on water temperature, swimming depth, and light levels. The tag is attached just below the dorsal fin and the leader extends away from the shark's body, allowing the tag to float along beside it. After a programmed period of time the tags pop off the fish, float to the surface, and transmit their data to satellite. From light level data (which tells us when the sun rises and sets) and sea surface temperatures recorded by the tag, it is possible to estimate the latitude and longitude and recreate the track of the animal. A Fast-GPS tag (another version of the PAT tag) is also used to tag basking sharks (Cetorhinus maximus). When the basking shark is swimming at the surface, the antenna should break the water's surface and communicate with satellites.
Smart Position and Temperature tag (SPOT tag)
The SPOT (Smart Position and Temperature) tag is attached to the dorsal fin and transmits the position of the shark when it is at the surface. The HMS Group started using satellite tags in 1999 to study the movements of sharks and was one of the first groups to mount SPOT tags to a shark’s dorsal fin.The SPOT tags have allowed us to track sharks for almost two years although most tracks are shorter. For many species, the satellite tags have provided, in just a few years, more data on movements and behaviors than had been collected over previous decades.
Check out the different types of tagging equipment in our image gallery!
The SPOT and PAT tags have provided some exciting insights into the biology of the blue, mako and thresher sharks and hundreds of tags have been deployed on all three species. To date, most sharks have been tagged in the southern California Bight and are juveniles. Historical data shows that the larger animals (greater than 200 centimeter fork length) retain the tag longer and provide us with longer time-series tracks. While all species utilize the coastal waters in the Southern California Bight and regularly cross the border into Mexico, key differences among years and species are apparent.
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|PAT tag data includes light level (sunset and sunrise) and sea surface temperature (SST), which allow scientists to estimate the latitude and longitude and recreate the track of the animal. Pictured here are comparative tracks of blue sharks (Prionace glauca) and shortfin mako shark (Isurus oxyrinchus) tagged over a span of three years in the Southern California Bight. These track models help researchers gain insight into shark behavior as it relates to environmental conditions for a given time period. || |
For example, over the period covered by the satellite tracks, the blue sharks tagged have traveled the farthest offshore to waters south of Hawaii. Movement patterns for mako sharks show distinct differences among years, as movements were much farther offshore in El Nino years and the shift in distribution likely reflects a change in the availability of food near-shore. An examination of daily dive patterns reveals some additional differences among the three species. In comparison to the mako sharks, the blue and thresher sharks show a distinct diurnal pattern. The greatest difference in day and nighttime depth distributions is apparent in thresher sharks, which spends more time at depth during the day than either of the other two species.
Combined data from many years suggest that both sexes of blue sharks spend considerable time in the California Current, with the females possibly extending farther north and south. When offshore, the females generally move south into the subtropical convergence zone, whereas the males make more westerly migrations. Habitat separation by both sex and site fidelity have implications for the management of blue shark populations. For example, fidelity to specific areas is increasingly recognized in fish from swordfish to salmon sharks (Lamna ditropis) and raises the potential for local depletion where fisheries exist. Age validation studies with oxytetracycline (OTC) thus far, indicate that a single band pair (1 translucent and 1 opaque) is formed per year for blue sharks of the size range examined. These preliminary results corroborate annual deposition rates found in the only other OTC validation study for blue sharks and should aid in future blue shark age and growth studies in the Pacific Ocean.
|The basking shark (Cetorhinus maximus) is often seen filter feeding on the surface in temperate coastal waters (left), however not much is known about its movements or distribution in the Pacific. In 2010, the SWFSC tagged the first basking shark in the Pacific and after 8 months at liberty, the PAT tag reported the fish had traveled from Southern California to a final location near Hawaii (right). |
Members of the Fisheries Resources Division of the SWFSC successfully tagged a basking shark off Point Loma in 2010, the first basking shark ever tagged in the Pacific Ocean! The basking shark is a large filter-feeding shark found in temperate coastal waters, usually basking and feeding on the surface near ocean current fronts. In the eastern Pacific Ocean, they are usually seen off the coast of Canada and Central California, however not much is known about their habitat utilization, population structure, or range of movements. The U.S. has teamed up with Mexico and Canada to place satellite tags on basking sharks to look at large scale movement. Since our first tagging in 2010, three basking sharks have been tagged since and one of the satellite-based tracking devices resurfaced near Hawaii after eight months collecting data on the migration. Read more about the basking shark tagging research...
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
8901 La Jolla Shores Dr.
La Jolla, CA 92037
Please contact us if you capture a shark tagged with a SWFSC conventional tag, PSAT, or SPOT tag. Find out more information about how and what to report and if a reward is offered.