Researchers at UH develop better tracking of ocean animals

Researchers working on a government-funded project said they’ve figured out a more accurate method to analyze animal movements in the ocean, including fish migration.

The new method could help provide researchers and marine managers with better analysis to support marine conservation activities for threatened species.

"The method can be used by anyone tracking animals in the sea with observing (sonar) networks," said Kevin Weng, manager of the University of Hawaii’s Pelagic Fisheries Research Program. "Knowing their movement helps us to better understand how they feed, breed and rest. Ultimately, more accurate movement information will help us to conserve these species."

Weng said the analytical method could be used to measure the statistical likelihood of fish movement in a general area.

Weng and researcher Martin Pedersen published the results this month in the peer-reviewed scientific journal Methods in Ecology and Evolution.

Weng said the Pelagic Fisheries Research Program developed the analytical method, and the field testing was funded through a $203,000 grant from the Coral Reef Conservation Program and Hawaii Undersea Research Lab, both operated by the National Oceanic and Atmospheric Administration.

Pedersen said researchers traditionally have considered only the places and time when a fish was detected.

Pedersen and Weng said the new method takes into consideration how far a fish could travel in a certain time since it was last heard and where it hasn’t traveled — information used to provide statistical probabilities of movements in a general zone.

"It tells us how the fish is moving," Pedersen said. "Does the fish swim in straight lines?Does it have a particular home range, or center of attraction, for its movements?"

Pedersen said the second part estimates the likelihood of detecting a fish based on probability, environmental noise, and the presence and absence of information.

The application of science is never easy when the site of the study is a remote atoll 1,000 miles south of Hawaii and the fish species to be studied requires diving in reef conditions where divers expect to see sharks.

The scientific team set up 51 underwater listening stations around Palmyra Atoll for the two-year study. The team caught 19 humphead wrasse, sedated them, and surgically implanted tracking devices.

During the surgery, water with a lot of oxygen was pumped through a hose into the mouth of the fish.

Weng said the operation has to be quick to prevent the fish going into shock.

"You’re holding this fish in your hand. Every one of those animals is so precious," he said. "You’ve got to have everything planned. You’ve got to have all your plans wired."

The 19 wrasse ranged from a foot to about 3 1⁄2 feet long, he said.

Weng said the humphead wrasse, Cheilinus undulatus, being considered as a federal threatened species, can live for a relatively long time.

One of the wrasse they tagged was 15 to 20 years old, Weng said.

"It’s incredible how long that fish can live," he said.

Weng said few are found in populated islands like Kiribati but are more plentiful at Palmyra, where fishing is banned and wildlife is protected by the federal government.

"It’s one of the rare areas on planet Earth where there’s very little footprints of humans," he said.