Tracking data off the western coast of the United States showed how advanced mako sharks’ sense of navigation and site memory really is.
Researchers from NOAA Fisheries, Stanford University, Tagging of Pacific Predators, and the Center for Scientific Research and Higher Education in Baja California tracked 105 mako sharks tagged with satellite tracking devices over 12 years—from 2002 to 2014 — to find that despite traveling up to 12,000 miles of the Pacific each year, they instinctively know where to return to find food and points of aggregation. The study, published in the most recent issue of the journal Animal Biotelemetry, revealed the sharks’ behaviors when they ventured outside the Southern California Bight. They found that the makos returned to familiar offshore areas year after year.
“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.”
The researchers used two types of tags to track the sharks including 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.The tagging data showed that the sharks travelled as far north as Washington, as far south as Baja California, and westward across the Pacific as far as Hawaii.
Despite their lengthy travels, most of the juvenile sharks that began in the Southern California Bight returned annually in summer when the waters are most productive for potential prey.
“If you have some memory of where food should be, it makes sense to go back there,” said Heidi Dewar, a research fisheries biologist at NOAA Fisheries’ Southwest Fisheries Science Center in La Jolla, California.. “The more we look at the data, the more we find that there is a pattern behind their movements.”
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.”