Shark populations rely on healthy reefs, but with so much damage to our reefs in recent years, a new study is focusing on how to protect sharks.

The results from an eight-year shark tagging project at Palmyra Atoll, an isolated national wildlife refuge 1,000 miles south of Hawaii, has established a much needed baseline for what constitutes a healthy shark population.

Led by The Nature Conservancy and the University of California at Santa Barbara, the study indicates a healthy shark population can be smaller in size than originally thought.

Dr. Eric Conklin, director of marine science for The Nature Conservancy, says “we did the study in parts to understand specifically the sharks, how healthy that population is and use that as a guidepost for what conservation efforts in other places should be aimed for.”

Researchers tagged 1,300 reef sharks during the eight-year project and recaptured 350. Conklin says that’s the largest shark tag capture in the world.

“The numbers that we found there are still far, far, far greater than what you will find in the main Hawaiian islands here,” he said, “and so that does tell us that that is a really critical part of our ocean resources here that we have lost, and knowing just how much we have lost gives us an idea of what we need to work to restore.”

Shark populations can be built up by establishing marine managed areas. “Big shark populations need healthy reefs in order to survive and thrive,” Conklin said, “so part of it is also making sure that the reefs that the sharks are reliant on are healthy, and that gets back to making sure that what we are doing on land isn’t affecting the reefs, that there is clean, clear water on our reefs, and what we are harvesting from the reef is sustainable and leaves enough behind so that the reef can continue to support itself.”

The research could make a huge difference as Conklin says some shark species have seen as much as 90 percent of their population disappear.

Conklin says the discrepancy between the study’s findings and earlier visual estimates is likely due to behavioral factors, not a decline in the atoll’s shark populations. “When marine scientists first began conducting research at Palmyra, they would be surrounded by sharks whenever they jumped in the water,” he said. “But over time, as the sharks have become accustomed to seeing people, they are no longer quite as curious about our presence.”

Palmyra Atoll, a Nature Conservancy preserve and a U.S. Fish & Wildlife Service national wildlife refuge with 15,000 acres of surrounding coral reefs, is one of the few places left where sharks and other large apex predators dominate the marine ecosystem. The refuge is off limits to commercial fishing, and with the exception of its occupation by the U.S. military in World War II, has never had a permanent human settlement.