December 10, 2023

Sharks may hold key to hurricane forecasts

sfl-shark-tagging-technology-20140218By Ken Kaye, From Sun Sentinel

They’re called ocean weathermen.

More than 750 sharks, tarpon, tuna and billfish, fitted with satellite-linked tags, are providing scientists with data on temperature and salinity at various depths in the Atlantic, Gulf and Caribbean. It’s information they hope could someday be used to improve hurricane forecasts, since a storm’s strength largely depends on how much warm water it will encounter.

“What the fish are providing is a profile of the ocean’s heat structure,” said Jerald Ault, a marine biology professor at the University of Miami. “You get a picture of what the upper layers of the ocean look like.”

Ault and other scientists at UM’s Rosenstiel School of Marine & Atmospheric Science started tagging tarpon in 2001 and sharks in 2010 to learn more about migration, feeding and reproduction. About three years ago, they discovered a remarkable pattern: the fish remained in waters that were about 79 degrees, the minimum required for tropical systems to develop.

In addition, many swam into the waters around tropical systems, which churned up nutrients and made hunting for food easier.

That’s when scientists realized that fish could provide accurate ocean temperatures, which could be fed into the computer models that forecasters use to develop tropical predictions.

“The beauty of this is the fish can give a gazillion pieces of information, and that represents a really exciting opportunity,” said Nick Shay, a professor of meteorology and oceanography at Rosenstiel.

Eventually, the UM scientists would like to feed the data from the fish to the National Hurricane Center. But to harvest enough data would require thousands of tagged fish swimming through all tropical regions, Ault said. That’s why UM is trying to secure more funding from both private and government sources.

The hurricane center was noncommittal, saying it did not expect the fish to have “a significant influence on hurricane forecasting,” according to James Franklin, the center’s top hurricane specialist.

But the UM scientists are convinced of the potential and plan to expand their fish tagging program. The tags are programmed to detach after a set period — usually one to two years — then float to the surface and automatically beam data to satellites.

However, the tags also are designed to immediately release their information to a satellite anytime a fish comes near or breaks the surface, and that happens often, Ault said.

“Most of these animals travel 30 to 100 miles a day, and that’s a long ways to go without coming near the surface at some point,” he said.

After the data is transmitted to a satellite, it is then relayed to the UM scientists.

The tag data shows many fish followed a temperature trail where the water was 79 degrees and sometimes swam directly into the paths of storms, Shay said.

For instance, a Blue Marlin in September 2004 swam under Hurricane Ivan in the Gulf of Mexico. A tarpon did the same thing with Hurricane Katrina the following season.

“It became really clear with the Ivan case how valuable this information could be,” Shay said.

Part of what makes fish such effective sentinels is that they make “yo-yo” motions as they search for food, said Neil Hammerschlag, a research assistant professor at Rosenstiel.

“They’re going up and down and up and down,” he said. “They’re continuously sampling the water, and that provides a structure that you would never see.”

Some sharks, such as nurse sharks, might provide an early warning that a strong storm is in the making, as they tend to run when a system’s internal pressure is dropping.

“It’s like a canary in the coal mine,” Hammerschlag said.

UM scientists note fish are able to obtain better information than “gliders,” small underwater vehicles that the National Oceanic and Atmospheric Administration began using in 2012 to boost hurricane forecasts. The aquatic drones, also satellite linked, are placed in the vicinity of storms to measure ocean heat.

The problem is the gliders move slowly and only in the same direction as ocean currents, while fish can swim swiftly upstream toward a storm.

Gliders also cost about $200,000 apiece, compared to about $4,000 per fish tag. “The fish give higher resolution information,” Shay said.

Tagging the fish, including bull sharks, hammerheads and tiger sharks, can be time-consuming and tricky.

To find the fish, the scientists cooperate with boats in fishing tournaments and otherwise spend hours trolling everywhere from Latin America to the Atlantic. After a fish is caught, it must be quickly tagged and released to ensure it returns to the water healthy, Ault said.

“It’s a little like a NASCAR tire change; the fish is brought into the boat, tagged and released,” he said. “You’re putting that expensive bling on it, so you want to make sure it survives.”

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