A 2017-2020 restoration project was plagued by rain, king tides, and storms, including Hurricane Lane, but researchers believe the ponds themselves “can support good growth rates and good survival.”

The ponds are a model of sustainability: often built at the mouths of streams, they support fish that feed on algae and seaweed in the silty environment.

Unlike contemporary aquaculture systems, they require no input of feed and are largely self-sustaining, needing minimal management and maintenance once established.

OAHU, Hawaii — Tucked at the base of the Ko’olau Mountains on the eastern side of the Hawaiian island of Oahu lies He’eia fishpond. Built around 800 years ago by indigenous Hawaiians, it was a thriving aquaculture site for hundreds of years, before falling into disrepair after a flood damaged its wall in 1965. Fishponds had been declining even before then; culture and land use patterns started to change with the arrival of Captain James Cook in 1778.

Ancient Hawaiians originally built almost 500 fishponds throughout the Hawaiian islands. At the time, they managed to support themselves entirely from the ponds, island agriculture, and occasional forays into the ocean for offshore fish.

Today, 87% of Hawaii’s food is imported, including 63% of its seafood. Of the original 488 ponds, 20 have received restoration permits through the state of Hawaii. However, it’s difficult to determine an exact number. Some ponds have had only minor restoration work done, and don’t have a permit. At 36 hectares (88 acres) and with a perimeter of 2.1 kilometers (1.3 miles), He’eia is one of the largest.

In 2017, the National Oceanic and Atmospheric Administration (NOAA) awarded a Saltonsall-Kennedy grant to the Oceanic Institute at Hawaii Pacific University (HPU) and Conservation International. The goal for the grant was to study the logistics of producing fish at three fishponds, including He’eia, and determine whether they could again be turned into productive aquaculture sites.

The three-year project was just completed. So was it a success? Yes and no, says principal investigator Chatham Callan, director of the Oceanic Institute’s finfish research program. “The project was successful in a lot of ways, but not in the ways we originally envisioned,” he told Mongabay in an interview recently.

Most fishponds have disappeared or are in varying states of disrepair, and those that have been restored are mainly used as cultural and educational resources. Researchers chose fishponds that had already received some restoration, and transported juvenile mullet from hatcheries to raise in the ponds. “The goal was to monitor those fish as they were growing and see what their growth rates were, what the survival rates would be, and that kind of thing,” Callan said. The fish were kept in small nursery ponds (pua in Hawaiian) so they would be easier to track. Each fishpond created a different setup according to its needs.

“Our approach here was not to be prescriptive, but to be supportive of what partners were wanting to do and learn,” said Ulu Ching, a senior program manager at Conservation International.

According to research results, some nurseries did well, but all were affected by “unprecedented” king tides, rains, and storms, Callan said. At He’eia, the nursery ponds may also have been too small, adds Hi’ilei Kawelo, executive director of Paepae o He’eia, the nonprofit organization that is working to revitalize He’eia fishpond. Long stretches of warm, cloudless days and low winds led to low oxygen levels for some fish, she said. To counteract this, she said she hopes to increase the flow of cooler freshwater streams into the pond.

“So it wasn’t a success as far as understanding the growth rates and how these fish survive in the best of conditions, because the nursery pens weren’t constructed in a way to deal with these changing weather events,” Callan said. Still, he added that, “We do believe that the fishponds themselves and in their current condition can support good growth rates and good survival.”

Cultural value

While producing fish is one of the goals for fishpond revitalization, their cultural significance is also important. Native Hawaiians were known for their environmentally friendly views and farming methods. They believed their health as a society was interdependent with the health of their land, and strove to live in a way that was in tune with the natural world.

Kawelo said she believes much of this perspective has been lost over the years. “In traditional agriculture, everything worked with the land. Today, everything we see around us, works contrary to the land,” she said. For example, streams are channeled and enclosed in concrete so that houses can be built nearby. “Whereas traditionally, you wouldn’t live next to the stream because you knew a flood could come through,” she said.

Ching echoes this sentiment: “You didn’t build a loko i’a [fishpond] just anywhere. Our kupuna [elders or ancestors] understood the dynamics of a natural system and altered it so that there was increased abundance in that area. So it’s a completely different way of looking at aquaculture and coastal management.”

There’s little question that aquaculture is needed.

A World Bank report found that 62% of seafood consumed worldwide by 2030 will come from aquaculture. “In some ways, aquaculture is perceived as a negative thing, but I think when done correctly it’s actually very positive and it’s going to be very necessary,” Callan said. The dilemma, he said, is how to farm fish in a sustainable way.

What’s striking about Hawaii’s previous agricultural independence, Callan says, is that while early scholars believed the islands’ population was relatively small, many researchers now believe that ancient Hawaii had a population of around 1 million people, close to its current level of 1.4 million, yet still managed to feed itself entirely from its own resources.

The fishponds are unique because they don’t require any additional feed to support the fish. In modern aquaculture, around 20 million tons of wild fish are used each year to create fish meal and fish oil, most of which is used to feed carnivorous fish such as salmon. The industry is currently exploring alternative feeds such as bugs and soybeans, as well as fish oil replacements. Another concern is the waste created from excess feed as well as the buildup of fish feces. Hawaiian ponds cultivate herbivorous fish that feed on seaweed and algae, and the tides flush out nutrient-rich water regularly, so the system doesn’t need additional input.

Coastal ponds like He’eia were often built at the mouths of streams, where they not only contain silt from the waterways, but cultivate fish in the nutrient-rich environment. The ponds consist of a boundary rock wall, interspersed with sluice gates that have narrow gaps in the fencing. These allow young fish to swim in, but keep predators out and grown fish from leaving. They also allow the tide to bring in fresh, oxygenated seawater, and then pull out pond water.

In addition to these ponds (loko kuapā), which were the most common, there were freshwater ponds built in taro patches (loko iʻa kalo) or in diverted streams (loko wai), as well as ponds separated from the ocean by a beach or sandbar (loko puʻuone).

Solutions

As pressures from climate change mount, it’s becoming more important to develop environmentally friendly food solutions. But that search will likely be multifaceted.

A key point is to ensure aquaculture is also sustainable “from a people perspective,” says Ching. “The intent is to support and feed people in our community. And so you need the environment to be maintained in order to do that. And you need the people to be maintained to do that. So the sustainability is in those two senses.”

She added that while there’s a lot to learn from ancient practices, “vice versa with contemporary methods.”

“[The project] was definitely helpful. And I think the people that participated learned a lot,” said Brenda Asuncion, coordinator at KUA, which means “back” in Hawaiian. KUA’s purpose is to encourage community-based management of natural and cultural resources in Hawaii, and support community organizations in this goal. One of the groups KUA facilitates is Hui Mālama Loko I’a, a group of fishpond practitioners whose work covers the three ponds in the study.

Still, she said, to truly see a change in mullet fisheries would take 10 to 15 years. In the past, pond nutrients would naturally draw in the fish. But wild mullet stock has plunged dramatically. “The wild fish that would have been feeding these fishponds are just no longer there. So that’s why a lot of people think hatcheries are needed now,” Asuncion said.

A three-year grant may sound like a long time, she added. “But then at the same time, the time for a mullet to get to a generous harvest size is one year. And then researchers also had to establish the holding ponds, and the hatchery had to figure out their system of producing the fingerlings. In that context three years goes by so fast,” she said. “The work that people are doing here is on the scale of maybe not even seeing the fruits of their labor in their lifetime.”

Both Kawelo and Asuncion added that popular taste has changed: many people don’t like the taste of herbivorous fish such as mullet, which were key in Hawaiian aquaculture. He’eia’s aquaculture practitioners didn’t close a final hole in the pond’s border wall until 2015, but still plan to eventually sell fish to the local community. They already sell Samoan crab to the public once per month. The fishpond consortium is also considering pooling their resources and trying another batch of mullet fingerlings.

For now, Kawelo continues to promote He’eia’s cultural and scientific value, and gets people off their phones and into nature. He’eia receives more than 10,000 visitors per year, and has hosted scientists from schools throughout the world. Would-be volunteers for restoration work must sign up at least three months in advance.

“What we’re trying to do [at He’eia] is grow the ability for people to think critically and innovatively, because I think the success of the future population of Hawai’i is going to depend on people that are tied closely to the land,” Kawelo said. “The solutions are going to come from the land, from being outside.”

Banner image: The fishpond at He’eia. Photo by Mark Lee.