Nav: Home

Mako shark tracking off west coast reveals 'impressive' memory and navigation

September 11, 2019

The largest effort ever to tag and track shortfin mako sharks off the West Coast has found that they can travel nearly 12,000 miles in a year. The sharks range far offshore, but regularly return to productive waters off Southern California, an important feeding and nursery area for the species.

The findings demonstrate "an impressive show of memory and navigation." The sharks maneuver through thousands of miles of the Pacific but return to where they have found food in years past, said Heidi Dewar, a research fisheries biologist at NOAA Fisheries' Southwest Fisheries Science Center in La Jolla, California.

Researchers tagged 105 mako sharks over 12 years--from 2002 to 2014. The tags record the sharks' movements, as well as the environments the sharks pass through. Researchers have long recognized that ocean waters from Santa Barbara south to San Diego, known as the Southern California Bight, are an important habitat for mako sharks. Prior to this study, however, they knew little about what the sharks do and where they went beyond those waters.

The researchers are from NOAA Fisheries, Stanford University, Tagging of Pacific Predators, and the Center for Scientific Research and Higher Education in Baja California. They reported their results in the journal Animal Biotelemetry.

"We did not know what their overall range was. Were there patterns that they followed?" asked Nicole Nasby-Lewis, a NOAA Fisheries research scientist at the Southwest Fisheries Science Center and lead author of the new research. "It turns out they have their own unique movement patterns." Sharks tracked over multiple years returned to the same offshore neighborhoods year after year.

Long-Range Travelers

The tagging data overall revealed that the sharks travel widely along the West Coast. They venture as far north as Washington, as far south as Baja California, and westward across the Pacific as far as Hawaii. The sharks tagged off California remained on the eastern side of the Pacific east of Hawaii. This indicates that they do not mix much with mako sharks in other parts of the Pacific.

Although there are examples of mako sharks crossing the ocean, it is probably the exception rather than the rule, said Dewar, a coauthor of the new research.

The finding provides insight into population dynamics of mako sharks across the Pacific. It also allows scientists to identify which fisheries the tagged mako sharks might encounter. Muscular mako sharks are a popular sport fishing target. They are also caught in U.S. longline and drift gillnet fisheries and are common in the international trade in shark fins. Mako sharks are overfished in the Atlantic Ocean, but not in the Pacific.

The researchers used two types of tags to track the sharks. One type, called pop-up tags, collect data and eventually pop off the animal and float to the surface, where they transmit their data via satellite. The second type transmits data to satellites each time the shark surfaces, determining the animal's location by measuring tiny shifts in the frequency of the radio transmission.

Remembering Southern California

Mako sharks are among the fastest swimmers in the ocean, hitting top speeds of more than 40 miles per hour. The larger tagged sharks traveled an average of about 20 miles a day and a maximum of about 90 miles per day. They travel long distances in part because they must swim to move water through their gills so they can breathe, Dewar said.

Large numbers of juvenile sharks caught in the Southern California Bight indicate that it is a nursery area for the species. Tagged mako sharks returned there annually, most typically in summer when the waters are most productive. The tracks of the tagged sharks may look at first like random zig-zags across the ocean, Dewar said. They actually illustrate the sharks searching for food and mates based on what they remember from previous years.

"If you have some memory of where food should be, it makes sense to go back there," Dewar said. "The more we look at the data, the more we find that there is a pattern behind their movements."

The tagging results also provide a wealth of data that scientists can continue to plumb for details of the sharks' biology and behavior. About 90 percent of the time the sharks remained in the top 160 feet of ocean, for example, occasionally diving as deep as 2,300 feet. Although the sharks traveled widely, they mainly stayed in areas with sea surface temperatures between about 60 and 70 degrees Fahrenheit.

"We can continue to ask new questions of the data to understand these unique movement patterns," Nasby-Lucas said. "There's a lot more to learn."
-end-


NOAA Fisheries West Coast Region

Related Fisheries Articles:

Fisheries management is actually working, global analysis shows
Nearly half of the fish caught worldwide are from stocks that are scientifically monitored and, on average, are increasing in abundance.
Meeting the challenges facing fisheries climate risk insurance
Insurance schemes with the potential to improve the resilience of global fisheries face a host of future challenges, researchers say.
Healthy mangroves help coral reef fisheries under climate stress
Healthy mangroves can help fight the consequences of climate change on coral reef fisheries, according to a University of Queensland-led study.
Study champions inland fisheries as rural nutrition hero
Researchers from MSU and the FAO synthesize new data and assessment methods to show how freshwater fish feed poor rural populations in many areas of the world.
For global fisheries, it's a small world after all
Even though many nations manage their fish stocks as if they were local resources, marine fisheries and fish populations are a single, highly interconnected and globally shared resource, a new study emphasizes.
New study maps how ocean currents connect the world's fisheries
It's a small world after all -- especially when it comes to marine fisheries, with a new study revealing they form a single network, with over $10 billion worth of fish each year being caught in a country other than the one in which it spawned.
Federal subsidies for US commercial fisheries should be rejected
A pending rule change proposed by the US National Marine Fisheries Service would allow the use of public funds to underwrite low-interest loans for the construction of new commercial fishing vessels.
Sustainable fisheries and conservation policy
There are roughly five times as many recreational fishers as commercial fishers throughout the world.
For the fisheries of the future, some species are in hot water
Some fisheries may falter while others could become more productive as the world's waters continue to warm, according to a new study, which looks to the productivity of fisheries in the past to help predict the impact of climate change on future fisheries.
'Dead zone' volume more important than area to fish, fisheries
A new study suggests that measuring the volume rather than the area of the Gulf of Mexico's dead zone is more appropriate for monitoring its effects on marine organisms.
More Fisheries News and Fisheries Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Reinvention
Change is hard, but it's also an opportunity to discover and reimagine what you thought you knew. From our economy, to music, to even ourselves–this hour TED speakers explore the power of reinvention. Guests include OK Go lead singer Damian Kulash Jr., former college gymnastics coach Valorie Kondos Field, Stockton Mayor Michael Tubbs, and entrepreneur Nick Hanauer.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at Radiolab.org/donate.