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Expedition gives researchers new information about opihi


Stephens Media

Researchers in the Northwestern Hawaiian Islands picked up some new information about one of Hawaii’s favorite little invertebrates, including an observation that females live higher up in intertidal zones than males.

An expedition team including scientists from the National Oceanic and Atmospheric Administration and Texas A&M University returned to Oahu this week, after the trip to the Papahanoumokuakea National Marine Monument to study the intertidal zone in the islands. While there, they focused on opihi, the popular limpets Hawaiians prize for eating at luau, weddings and graduation parties, expedition leader Hoku Johnson said.

The marine monument area is a great place to study opihi, said Johnson, who is NOAA’s planning and evaluation coordinator and works in the Office of National Marine Sanctuaries.

“Because it’s so highly protected, we can learn a lot about the life history of the opihi,” she said. “It’s like a new frontier for us.”

Opihi are rarely found in accessible areas in the main Hawaiian Islands anymore, she said.

The apparent separation of opihi by sex is preliminary, Johnson said. But if confirmed, it could help scientists put together better rules for managing — and encouraging a resurgence of — opihi around the state, she added. One possible way to protect opihi might be limiting harvest of the species from broad areas that include both the higher locations where females may congregate and the lower areas where males were found, she said. Scientists may also consider recommending seasonal or stricter size restrictions, she added.

Getting the information was especially difficult in the Northwestern Hawaiian Islands because of the inherent risks involved in looking for opihi, Johnson said. Every few years, if not more frequently, someone on Hawaii Island is swept out to sea while picking opihi along remote, steep shorelines. Working in the Northwestern Hawaiian Island’s rocky coastal areas was difficult and dangerous, but researchers mitigated the risks in part by having a boat off shore, ready to provide emergency assistance if necessary, she said.

The team spent 12 days on the shorelines of Nihoa Island, Mokumanamana Island, and French Frigate Shoals, part of the Hawaiian Islands National Wildlife Refuge within Papahanaumokuakea.

Scientists also conducted research into a hypothesis relating to why opihi in the main Hawaiian Islands reproduce at a smaller size than those in the Northwestern Hawaiian Islands. Scientists said that shows more pressure from fisheries closer to the main islands forces opihi to reproduce at an earlier and smaller life stage.

Right now, opihi gathering practices are proving to be unsustainable, Johnson said.

“Opihi are something that bring people together,” she said. “If we can manage the right way, we can have opihi forever.”

Email Erin Miller at emiller@westhawaiitoday.com.


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