Researchers on small boats catch a Black Reef Shark, one of the major predators in the waters around Palmyra. Credit: Mark Shwartz, Stanford News Service/Woods Institute for the Environment at Stanford.
In Palmyra Atoll, scientists are taking advantage of technology to help them track the movements of sharks, birds, fish and other animals. They use tiny devices, called tags, to record or transmit data.
But the fish and birds must be caught before they can be tagged, and some, like sharks, are more challenging to get hold of than others.
The information transmitted by the tags is important because the shallow waters of the reef get very warm, especially at low tide, and that can be tough on marine life. Researchers want to know how sharks in this Pacific Ocean lagoon are coping with increased water temperatures.
The Shark Team
Alan Freidlander, a scientist with the National Oceanographic and Atmospheric Administration, is part of a team heading out to catch sharks.
Outside the laboratory building on the atoll, he files away at a good-sized fish hook, trying to remove the barb. It's a preventive measure. The barbs tend to get stuck in the shark's mouth — which can be a bad thing for the person who has to remove the hook.
Inside the lab, another shark scientist, Chris Lowe, prepares for the hunt.
Lowe, a professor at California State University at Long Beach, is programming an acoustic receiver for a tag that will detect the temperature and depth of the water when it is in the shark. It also allows the researchers to track the animal's movements.
"We can not only follow it around and figure where it is and where it's moving along the edge of the reef, but we'll know how deep it is in the water column, and will know how warm its body is," Lowe says.
The Great Shark Hunt
The team of researchers heads out in a small boat to the edge of the reef to catch and tag sharks. Lowe and Friedlander are accompanied by Jennifer Cassele of the University of California at Santa Barbara, and Yannis Papastanatiou from the University of Hawaii.
They begin by chumming with a little squid, and right away, the dorsal fins start circling. The team is looking for a Black-tipped reef shark, not too big and not too small. Yannis says that a meter long is the ideal size – big enough to handle the tag implant, but not too big for the researchers to handle.
Suddenly, a shark appears right by the boat. Yannis takes the hook, and there is a burst of activity as the researchers work the shark to the side of the boat, slip a noose around its tailfin, and very carefully try to turn it over on his back.
The sharks go into a kind of trance and become immobilized when they are placed belly up.
Yannis leans over the boat with a scalpel in his hand.
"I'm just making a small incision in the wall of the abdomen so we can insert the transmitter," Yannis explains.
He notes this shark is a female, and slips in the transmitter. It's about the size of a small, disposable cigarette lighter. Yannis ties one quick stitch where he made the incision. The scientists test the transmitter, then flip the shark over and release it.
Palmyra's Unique Research Conditions
These scientists say that Palmyra is critical to their work. In most other places, Lowe says, sharks have been so depleted by over-fishing, development, and pollution that it's difficult to isolate how they are responding to changes in climate.
"But here you have as pristine area as you can find," Lowe says. "So despite the fact that climate change may be occurring as a result of humans, we're still able to get an idea of how the animals are responding based on what are going to probably be more rapid changes in climate."
During their week on Palmyra, the shark researchers tagged dozens of sharks, and they left behind data loggers that will record the sharks' movements over the course of the next year. Then, they'll return to collect the data and, from it, learn more about these predators that sit at the very top of a very long ocean food chain.