Scientists know why Maui leads in shark attacks

There’s a reason Maui sees more shark attacks than any other Hawaiian island, according to the results of a new study: It’s the large and protected shallow ocean shelf that acts as a magnet for tiger sharks near and far.

In addition, the most visited waters by tiger sharks around Maui include some of the most popular beaches and ocean recreation sites, the study said.

It’s that combination of factors that point to why Maui has more shark bites, according to the study, although researchers cannot entirely rule out a higher number of ocean recreation activities on Maui as the primary cause of the recent bump in the number of shark attacks.

“Over the past 20 years, Maui has had almost double the number of shark bites of any other island, even though all of the larger islands have thousands of people going into the ocean every day,” University of Hawaii researcher Carl Meyer said at a news conference Thursday.

Meyer’s UH Institute of Marine Biology research team used a combination of satellite and acoustic tracking to monitor the movement of 41 tiger sharks around Maui and Oahu for up to two years.

The $186,000 study was commissioned by the state Department of Land and Natural Resources following a spike in shark bites off Maui in 2012 and 2013.

Meyer, principal investigator of the study, said the ocean around Maui, Molokai, Lanai and Kahoolawe has more preferred tiger shark habitat than all the other main Hawaiian Islands combined.

The vast shelf area of reef habitat around Maui extends offshore to depths of 600 feet and is home to a wide variety of tiger shark prey, he said. The shelf area is also ideal for tiger shark mating and pupping.

The study’s tracking data indicate that individual sharks visit Maui more often than they visit the other islands — about 2.5 times per month compared with 1.5 times a month for Oahu and about once every two months for Kauai and Hawaii island.

What’s more, many more sharks were detected per day in Maui waters than in Oahu waters, according to the study’s acoustic tracking. Off southwestern Maui, tiger sharks were present more than 80 percent of the time.

“That equates to a near daily presence of these large tiger sharks at ocean recreation sites,” Meyer said. “But it’s important to remember that even though there is nearly a daily presence of these animals, there are thousands of people going into the water around Maui, yet shark bites remain rare events.”

The data suggest that tiger sharks generally avoid interactions with people, he said.

The study also found that tiger sharks visit near-shore waters at all times of the day and night, which would suggest there’s no greater chance of getting attacked at sunset or during the night.

The pattern of shark bites, Meyer said, matches human behavior, with 70 percent of the bites occurring between 9 a.m. and 4 p.m.

Maui-tagged sharks did not visit Oahu, Meyer said, but Oahu-tagged sharks visited Maui waters in greater numbers during the core winter months, which is the peak mating season. Previous studies indicated that tiger sharks from even the farthest regions of the island chain also gravitate to Maui for reproductive reasons.

Meyer rejected measures such as shark culling, shark nets and real-time monitoring warning systems as useless and unnecessary. Previous shark hunts in Hawaii didn’t reduce shark attacks, he said, and only resulted in new sharks filling the void.

Bruce Anderson, administrator of DLNR’s Division of Aquatic Resources, said the department commissioned the study out of concern for public safety during a time when little information was known about why the sharks were behaving the way they were.

“The results reinforce the direction we’ve been taking for quite a while,” Anderson said. We’ve been recommending preventive measures rather than culling sharks.”

Preventive measures, he said, include staying out of the water if it’s murky, swimming with others and staying close to shore.

Anderson said changing ocean behaviors have contributed to the increase in shark bites over the last 20 years. More people are kayaking, blue-water spearfishing, stand-up paddling and swimming offshore, he said.

“Swimming in the ocean is what amounts to swimming in a wilderness-type environment,” Anderson said. “Sharks are part of this environment. We have to accept that they are there and take precautions to avoid encounters that are going to occur from time to time.”

Meyer said the reasons for the 2012-14 spike in shark attacks around Maui remain unclear. There was only one unprovoked shark attack off Maui in 2015, he said, yet there was no change in shark behavior and no shift in human behavior.

These spikes occur all over the world and are most likely due to chance, he said.

Historically, Hawaii averaged between two and three shark attacks a year going back to the 1980s. During the past two decades, the annual average edged up to between three and four shark attacks.

The Pacific Islands Ocean Observing System hosts a website, pacioos.org/projects/sharks, that shows the study’s tiger shark movements online.