'Opihi overharvesting means slim pickings

By Jan TenBruggencate
Advertiser Science Writer

Scientists fear that the largest and most prized species of the hardy 'opihi — a uniquely Hawaiian delicacy — may be essentially extinct on O'ahu, and the population of other limpets statewide is also on the decline.

The three species of 'opihi have distinctly different coloration. These specimens are all of legal size for harvesting. The Hawaiian name for the 'opihi at top, with green border, is makaiauli; right with yellow foot, is 'alinalina; left, with gray foot, is ko'ele. Jan TenBruggencate • The Honolulu Advertiser

"We don't sell it anymore. It's just too hard to get," said William Alana, owner of Da Pokeman Fish Market in Wahiawa.

Alana said his market bought 'opihi from a source on the Big Island until about two years ago, when they were told it was too hard to find.

"On O'ahu, you can't find it. On the Neighbor Islands sometimes you can — but the prices they get, it's like gold," he said. "And they have to go to really dangerous places to find them."

University of Hawai'i botanist Chris Bird said he recently visited the rocky shore below Princeville at Hanalei on Kaua'i.

"It was getting hammered by 'opihi pickers. There were virtually no legal 'opihi, and I still saw four people picking," he said.

But there still were plenty of small ones, perhaps because when winter surf makes the nearby Na Pali Coast cliffs impossible to approach, that area serves as a safe breeding ground that resupplies neighboring areas with larvae.

A century ago, 'opihi pickers were selling 140,000 pounds of the limpets annually. In recent years the number has been less than 10 percent of that, around 13,000 pounds.

"If you use the commercial catch as an indication of overall population size, the numbers are not decreasing anymore, but that may be because what's left is so hard to find," Bird said. As a botanist, Bird studies seaweeds, but because 'opihi eat seaweeds, he has become an expert in their biology as well.

Who eats 'opihi

Hawaiian 'opihi are an acquired taste — a crunchy, salty limpet vaguely reminiscent of abalone. They are generally eaten raw, either alone or mixed with flavorful seaweeds in a poke dish. Some afficionados prefer their 'opihi grilled in the shell over a driftwood fire, flavored with a little butter and garlic.

'Opihi can camouflage themselves against the background, their dark or light shell colors mimicking the rock, and they can sometimes grow seaweed on their shells that matches the surrounding environment. Jan TenBruggencate • The Honolulu Advertiser

Retired University of Hawai'i zoology professor and 'opihi expert E. Alison Kay, who has collected and eaten 'opihi since she was a child, said that in her decades of research, she found no Pacific culture that prizes limpets as much as Hawaiians do.

Kay said has she watched the decline in numbers over the past half century.

"Over the years, they've been getting fewer and fewer," she said.

Hawai'i's edible 'opihi are genuinely Hawaiian. All three species have evolved into unique forms here. Bird said that genetic studies suggest they are most closely related to a Japan limpet, suggesting an Asian origin for the Hawaiian limpets.

It's not clear how the first ones got here. The larvae are not very long-lived and probably could not have survived in the open ocean long enough to settle. That suggests immature or adult animals made the passage, perhaps clinging to a rock caught in roots of a drifting tree, a piece of floating pumice or driftwood.

"They would have to have been on something. I have seen an 'opihi on a piece of wood, a branch, but not often," Kay said.

Bird said the genetic work he and colleagues have done indicates that the less-favored black-footed 'opihi, makaiauli, evolved into a unique species earlier than the others.

It isn't clear whether the others evolved from that or from a separate introduction from Asia, but the yellowfoot 'opihi or 'alinalina and the bigger kneecap 'opihi or ko'ele appear to have evolved into their present form about the same time, he said.

Cross-breeding

Although the different species have different life cycles and may spawn at different times, they are closely enough related that they can cross. Bird said he has created hybrids in his laboratory. It also may be possible that crossbreeding between species occurs occasionally in the wild, said Celia Smith, the UH botany professor who oversees Bird's work.

Bird said the genetic work shows that the smaller two species — the blackfoot and yellowfoot — are closely related throughout the Hawaiian Islands, indicating their larvae traveled between the Hawaiian Islands.

But the populations of the big ko'ele, which can grow to be the size of a fist, seem to be isolated, so there doesn't appear to be much genetic mixing between, say, the Moloka'i ones and the Kaua'i ones.

That may be why the population of this prized species has virtually disappeared on O'ahu — it has been drastically overharvested and is not being resupplied from other islands.

Bird said there is plenty of habitat for the animals. They live on rocky shorelines where the seaweed isn't too thick, and use a rasping tongue to feed on coral-line algae, cyanobacteria and other life on the rocks.

It is not clear how the larvae are transported, and Bird said he hopes to use genetic techniques to determine which coastlines in the islands are sources of 'opihi and which are simply recipients.

With that information, wildlife managers might be able to enhance populations simply by protecting the most valuable source shorelines from overcollection.

"In most places now, the 'opihi that can reproduce the best are being picked," he said.

Reach Jan TenBruggencate at jant@honoluluadvertiser.com or (808) 245-3074.