Scientists sink teeth into ‘opihi habitat

  • ʻOpihi ʻalinalina, popular Hawaiian delicacy, with distinctive yellow foot. Credit: Kanoe Morishige

Scientists are only now learning more about the lives of a sea snail prized as a traditional Native Hawaiian delicacy.

The ‘opihi ‘alinalina, also called the yellowfoot ‘opihi, has long held a significant place within the traditional Hawaiian diet, but basic facts about them, such as their lifespans, have been largely unknown until a recent study by the University of Hawaii at Manoa.

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“With humans, it’s easy to figure out our lifespans because there’s a lot of us and we can keep track of us,” said Erik Franklin, an associate research professor at UH’s School of Ocean and Earth Science and Technology’s Hawaii Institute of Marine Biology. “But with ocean animals, it’s always a lot more difficult to figure this out.”

By measuring the levels of certain oxygen isotopes within the shells of three yellowfoot ‘opihi specimens, researchers including Franklin were able to determine the average lifespan and growth rate of the mollusks: yellowfoot ‘opihi can live for as many as five years, and are fully mature within about nine months.

Franklin said this information is foundational for organizations in Hawaii to develop conservation plans for ‘opihi.

Over the past century, Franklin said the average catch size for ‘opihi fishers has diminished, and fishers themselves have reported a decline of abundance over the years. Although the species is not considered endangered, threatened or protected, Franklin said UH’s research could be used to eventually restock ‘opihi populations and manage them more effectively.

Franklin added that the research might help preserve the species from the worst impacts of climate change, as the rocky intertidal shores where the mollusks feed are some of the most susceptible to rising sea levels.

‘Opihi are subject to some conservation laws already. State laws prohibit the taking, selling or possession of any ‘opihi shell less than 1.25 inches in diameter, or ‘opihi meat less than a half-inch in diameter.

Violators of this law are guilty of a petty misdemeanor and can be subject to fines of more than $500 per violation. In July, a man was cited for harvesting 345 undersized ‘opihi at Onekahakaha Beach Park in Hilo.

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Meanwhile, harvesting ‘opihi carries other risks. Because of the treacherous shores where the mollusks can be found, ‘opihi pickers can easily be swept to sea. In 2020, the body of an ‘opihi picker was recovered from the sea near Hawaii Paradise Park after being swept into the ocean the day before. And in 2019, two pickers were swept to sea near Honokaa — one was rescued not long thereafter, but the other was never found.

Email Michael Brestovansky at mbrestovansky@hawaiitribune-herald.com.

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