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Story Publication logo October 10, 2022

Innovations in Ancient Aquaculture Could Bring Striped Mullet Back to the Dinner Table


Hawaiian fishponds are threatened by climate change. They can also mitigate it. How are their...


Recent developments in growing striped mullet could help conserve Hawaii’s oceans, establish food security and perpetuate Hawaiian culture — but can they overcome new challenges?

Fishermen used to sit on shorelines and catch striped mullet, then steam them for dinner. But these days, most keiki don’t know what steamed striped mullet tastes like, or even what a school of mullet looks like.

For the past two decades, the striped mullet population in Hawaii has been declining, which has disrupted culture and traditions as well as the natural balance of the marine ecosystem.

Two new projects aim to restore mullet populations. Kamehameha Schools Kumuola Marine Science Education Center in Hilo and a Hawaii Sea Grant partnership with Waikalua Loko in Kaneohe are building on decades of aquaculture and fishpond work, but their success depends on how they deal with today’s environmental and societal challenges, from climate change to funding.

Mullet are raised at the Loko Waka under stewardship of Seaside Restaurant in Hilo. Image by Grace Cajski / Civil Beat. United States, 2022.

The striped mullet is of such cultural, culinary and ecological importance that the Hawaiian language has a detailed vocabulary for the fish: baby mullet are pua ʻama, adult mullet are ʻamaʻama. When the mullet reach sexual maturity they’re ʻanae, and when these fish school, it’s an ʻanae holo.

Ancient Hawaiians saw ʻanae spawn in the ocean during winter. They noticed the pin-sized pua swim to nearshore estuaries and graze on phytoplankton and algae. After a couple years, the pua ʻama swam seawards to spawn.

These keen observers engineered loko iʻa, or fishponds, to leverage this behavior. A pond’s kuapa, or wall, encloses the rich nearshore estuary, and a makaha, or gate, allows pua ʻama to swim in while restraining the full-sized ʻamaʻama. Oftentimes, kiaʻi loko, or fishpond caretakers, would put pua ʻama in smaller, more protected ponds called pua ponds.

Thanks to this design, kiaʻi loko could easily fish out ʻamaʻama and feed their community. That’s not the case anymore.

When the environment was healthy, the ʻamaʻama flourished and the fishponds were full. In 1900, commercial fishermen caught more than 700,000 pounds of striped mullet.

“They looked like dark clouds in the sea.”

Fred Takebayashi

In the 1940s, Fred Takebayashi, who grew up on what used to be Mikiola fishpond in Kaneohe Bay, could catch 10,000 pua ʻama in half a day.

“They looked like dark clouds in the sea,” he said.

George Uyemura, a former caretaker at Molii Pond, just north of where Takebayashi worked, often heard the splash of mullet leaping out of the water.

Development has since degraded ʻamaʻama nurseries, as have invasive plants like the mangrove and California grass. And invasive predators, including toʻau (black snapper) and roi (peacock grouper), hunt the mullet.

By 1950, less than 40,000 pounds of ʻamaʻama were caught in Hawaii. Then, another mullet species invaded.

The kanda, which looks almost identical to the striped mullet, spawns year-round and matures more quickly than the striped mullet. It’s also smaller, and competes with the ʻamaʻama to eat the same small organisms on the seafloor.

By 2019, the annual commercial ʻamaʻama catch had dwindled to just 1,660 pounds, and today less than 20% of the mullet in Oahu’s fishponds are striped mullet.

Aquaculturists are trying to change that.

Hormone Injections

ʻAmaʻama aquaculture began in the 1960s at Oceanic Institute, a research facility now associated with Hawaii Pacific University. At the time, aquaculturists still didn’t know how to get adult mullet to spawn, or how to raise the resulting pua.

“The mullet would get to a certain point, and then they would stop developing,” said Vernon Sato, a phycologist, aquaculturist and fishpond adviser.

Research at Waikalua Loko will help determine the future of striped mullet in its waters. Image by Wende Nishimoto / Civil Beat. United States, 2022.

That’s when Oceanic Institute got into using hormones to push the fish into that final stage of maturation, he said.

The aquaculturists tried injecting the mullet with salmon and carp hormones to get them to spawn, which sometimes worked, but they still couldn’t determine the best dosage and timing. Scientific developments in the 1970s helped them overcome this hurdle, and the striped mullet successfully spawned. Oceanic Institute grew the pua ʻama, and now aquaculturists could grow striped mullet whenever they wanted.

But by this point, the ʻamaʻama decline was undeniable. The state appropriated funds for Oceanic Institute to develop a mullet stock enhancement program. Between June 1990 and August 1993, the state’s program released nearly 245,000 pua ʻama in Kaneohe Bay.

The Division of Aquatic Resources established the Mullet Stock Enhancement Program in Hilo in 1998, which released mullet for two years, but funding dried up in 2001.

‘Pua Boot Camp’

Once the mullet life cycle was closed and aquaculturists knew that hatchery fish could survive in the wild, fishpond caretakers became interested in supplementing their fishpond with hatchery-raised ʻamaʻama. But virtually all attempts to grow hatchery-raised mullet in fishponds failed.

“Those fish were too sensitive, dumb and easy to hunt,” said Keliʻi Kotubetey, assistant executive director at Heeia Pond on Oahu.

Kai Fox, Hawaii Sea Grant’s aquaculture extension specialist, said the pua were grossly immature. Fox realized there needed to be a place where “the fishies could grow up a little more” — a contemporary pua pond.

“This project represents layers and layers and layers of projects in the past,” Fox said.

Waikalua Loko and Hawaii Sea Grant are establishing a nursery for pua to grow in. Image by Grace Cajski / Civil Beat. United States, 2022.

Last September, Hawaii Sea Grant collaborated with Waikalua Loko, a 12-acre pond in Kaneohe Bay, to construct a land-based aquaculture facility to nurse hatchery-raised fish. They termed this nursery “Pua Boot Camp.” Within it, the pua ʻama can get bigger and acclimate to the pond’s salinity and bacteria.

The pua boot camp is expected to start growing ʻamaʻama in 2023 provided by Oceanic Institute. In the meantime, it will grow nenue, a native gray schooling fish, from the Kona-based hatchery Ocean Era. And the wastewater from the fish tanks will flow to another series of tanks to grow limu, and that wastewater will flow to tanks containing native oysters and sea cucumbers.

Once the pua ʻama are 6 inches long, they can be released into fishponds. Fox will release some into Waikalua Loko, and he’ll give the rest to other loko iʻa.

Pacific American Foundation, the nonprofit that operates the pond, will sell some limu and sea cucumber to achieve economic sustainability. The group hopes the pua boot camp can innovate, restore and stabilize the fishponds and Hawaii’s ecology while serving as a bridge between Indigenous wisdom and modern science and technology.

The foundation’s first 25 years of stewardship at Waikalua Loko were spent on restoration. The next 25 years will be spent trying to grow fish, according to Pacific American Foundation CEO Herb Lee.

“Growing food was the original purpose of the ponds, but none of the remaining ponds are able to do so as originally intended,” he said. “Why? It’s a simple answer. The ecology has changed.”

Changing Winds

Tourism and development have altered Oahu’s ecology to such an extent that hardly any pua ʻama swim into its remaining fishponds. That’s not the case elsewhere in the state.

ʻAmaʻama are relatively abundant around the Big Island. Fishponds in Hilo — including Loko Waka (under stewardship of Seaside Restaurant), Hale o Lono (under stewardship of the Edith Kanakaʻole Foundation), Honokea Loko (under stewardship of Hui Hoʻoleimaluo), and Waiahole and Kapalaho Loko (under stewardship of Kamehameha Schools Kumuola Marine Science Education Center) — can naturally recruit ʻamaʻama.

But the Big Island is changing.

“AirBnBs have come up, and people have moved in,” said Kamala Anthony, who founded the Keaukaha nonprofit Hui Hoʻoleimaluo. “New development is straining old infrastructure and pushing the natural environment to its limits.”

She said there’s also been a disconnect over time as people move away, leaving no one to care for the fishponds.

More tourism and more people mean more development — and that has compressed estuaries and polluted them. Fisheries have suffered as a result.

“In areas where you’d expect to catch fish, you’d be lucky to catch one,” said Troy Sakihara, an aquatic biologist for the Division of Aquatic Resources.

Kumuola Marine Education Center collects pua by the makaha and uses genetic testing to determine whether it’s pua ama or the invasive kanda pua. Image by Grace Cajski / Civil Beat. United States, 2022.

This has been the worst year for ʻamaʻama natural recruitment at Kumuola since 2019 when data-recording began. Only 234 pua have come into the pond, down from a high of 2,839 in 2020.

Despite the data’s short timespan, the 88% decline in recruitment is worrisome to biologists. “These are severe impacts,” said Luke Mead, director of Kumuola.

Kumuola has innovated a genetic barcoding technique to determine whether pua are native or invasive mullet. It found that only one in eight pua are ʻamaʻama. The rest are kanda. Although staggering, this preliminary data will help loko iʻa rebuild the knowledge base necessary to understand and rehabilitate resources in loko iʻa, and help inform next steps for growing striped mullet.

The abundance of ʻamaʻama across all islands also depends on the rate of climate change. Scientists predict that there will be a half-foot of sea level rise by 2030 and more than 3 feet by 2100. That would overtop most kuapa and threaten nearshore ʻamaʻama aquaculture work.

Aquaculturists have already reported incidents they attribute to climate change.

Ron Weidenbach, owner of Hawaii Fish Company on Oahu’s North Shore, has noticed the trade winds slowing down. Less wind means less oxygen getting dissolved in the water, which threatens fish.

In 2016, Waikalua Loko, the fishpond in Kaneohe Bay, reported a mini extinction of limu attributed in part to shifts in ocean temperature. That same year, extremely high tides buffeted the pond.

And unseasonably large waves linked to king tides have become a regularity. In Hilo, Luke Mead has observed king tides during the summer, in addition to less rainfall and more severe weather.

The future of the mullet in Hawaii is unclear, but Mead said there has to be hope.

“Our job is to innovate, create and build networks and collaborative relationships,” he said. “We do things pono. We do what we can do.”

Hawaii Grown” is funded in part by grants from the Stupski Foundation, Ulupono Fund at the Hawaii Community Foundation and the Frost Family Foundation. 



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