Fresh data from an ongoing study reveal the shark most likely to bite you likes hanging out in shallower waters. Consequently, its favorite destination is Maui.
Although the tiger — the most likely culprit in shark bites in Hawaii waters — routinely travels hundreds of miles, it seems to prefer the coastal shelf areas in depths of less than 600 feet, which might explain a high incidence of shark encounters off Maui County islands in 2012 and 2013.
Maui County islands have a larger coastal shelf — up to 10 miles offshore — than other major Hawaiian Islands, where the coastal shelf tends to be narrower, said shark scientist Carl Meyer, one of two internationally recognized shark experts conducting the study.
"What this study has done is really drawn back the veil on how the tiger shark uses the coastal habitats around Maui," Meyer said. "So we’ve gone from knowing very little to having a fairly robust pattern of tiger sharks around Maui."
This might indicate Maui’s coastal habitats can support larger populations of tiger sharks than equivalent habitats edging other islands, and may be an important area for tigers from neighbor islands for feeding or reproduction.
Meyer and Kim Holland, senior shark scientist at the University of Hawaii’s Hawai‘i Institute of Marine Biology, embarked on the two-year study in 2013, tracking the tigers after a cluster of shark bite incidents in Maui waters prompted concern for the public’s safety.
In 2013 eight of 14 shark encounters — two fatal — occurred in Maui waters. The year before, seven of 11 encounters were in Maui waters, with one off Lanai.
Scientists started the study by tagging 18 large tiger sharks taken from Maui waters with satellite tracking devices. Last month they tagged eight off Oahu and mapped their tracks. (A total of 24 were tagged off Maui and 11 off Oahu, but some were fixed with only an acoustic device; others were double-tagged with acoustic and satellite devices.)
Each time a tagged shark was detected by satellite, it received a circle on the map. The study’s mapping shows waters between Maui, Lanai and Kahoolawe clogged with overlapping circles. Numerous detections were found around Molokai as well.
Oahu’s North Shore also shows a concentration of detections, but few were found elsewhere around the island. Oahu’s results are preliminary, and more animals will be tagged in the coming weeks and months off the island’s shores.
Both Oahu and Maui have high levels of recreational use, "yet Maui has a higher rate of shark bites. We are trying to determine why," Holland said in a news release.
"We are seeing the exact same depth preferences around Oahu, but the most frequently used sites don’t line up with popular swimming and surfing sites to the extent that they do around Maui," he said.
Meyer said, "For most of this year, nobody had been bitten by a shark on Maui, but during the whole time large tiger sharks were present in those coastal habitats. … The variations we see is best explained by chance."
Meyers said the tiger shark is "very surface-oriented," with "vertical behavior, yo-yoing" down from the reef to the surface, where they often capture their prey and investigate objects.
He pointed out that the most recent Maui shark bites occurred in murky water after heavy rain, when runoff debris can attract sharks.
A professional surfer and his three young sons were surfing in Hurricane Ana-generated surf off Maalaea on Oct. 18 when a 12- to 15-foot tiger shark charged the man. The surfer and his sons escaped injury, but the shark bit the surfer’s board.
Meyer, who has studied tiger sharks for 20 years, said the data are yielding valuable information.
The shelf habitat may be suitable for mating and pupping (newborns have been caught in 80- to 300-foot depths) and is presumably a good feeding ground since tigers have the most varied diet of any shark, feeding on reef fishes and other reef creatures. As they grow, they consume octopus, crabs, some birds and mammals. Larger tigers feed on other sharks (including tigers), rays and, to a small extent, turtles.
The data show some sharks swim 1,000 miles into the open ocean and come back, and maintain high use of coastal habitats. Of the eight tagged around Oahu, some have traveled around Maui.
Previous acoustic data show some sharks tagged around Oahu have made multiple trips back and forth between Oahu and Maui. One shark tracked over 51⁄2 years made a half-dozen trips between Maui and Oahu before going undetected for two years, indicating travel well outside the main Hawaiian Island chain. Another tiger shark was caught off the reef runway in Honolulu, caught a year later at the same location, then caught 18 months later by fishermen in the Sea of Cortez.
Additional funding is coming from the Pacific Islands Ocean Observing System and from the state to purchase some shark cameras, which will help the scientists better understand why these sharks like these coastal areas.
The shark cams, roughly the size of permanent-marker pens, will be attached with a timed release, which will release and float to the surface. They then will be collected and their information will be downloaded.
Tiger shark tracks are online at www.pacioos.org/projects/sharks.
