To assist Hawaii feed itself, scientists are utilizing trendy expertise to revive 2,000-year-old fish ponds

With the arrival of British Captain James Cook in 1778, growing sugar, pineapple, papaya and rice became big business in Hawaii. As a result, fewer hands were available to maintain fish ponds and they were no longer used. Other factors such as sediment accumulation, invasive mangroves, land use changes, and lava and tsunamis also contributed to the decline in fish ponds.

There are several common types of fish ponds in Hawaii. Loko kuapā are the most common type, with wooden sluice gates, or mākāhā, which allow small fish such as mullet to enter the pond and eat until they are too big to get through the gate and return to the sea. At this point, they can easily be harvested with nets.

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The fish pond style of Loko ea is the Loko puʻuone – isolated, natural bank ponds that are connected to the sea via an artificial sandbank channel. Other varieties include the Loko iʻa Kalo version, built alongside streams that flow into a cultivated, flooded terrace where taro grows. The fish live and feed between the taro patches, optimal habitats that are rich in food. And in another version of fish ponds, the Loko Wai, streams are diverted into natural depressions to create freshwater ponds inland.

Ancient techniques for modern use

Loko ea’s goal is to be a fully functional fish pond by the end of 2021. The next goal will be to get Uko’a, a much larger fish pond about a mile north, up and running. These follow the commercially successful Moli’i fish pond adjacent to Kaneohe Bay and the ongoing project in He’eia – an 800 year old pond with a 1.3 mile long lava rock wall.

Adapting old fish ponds to the modern world is possible, but challenging, according to the Oceanic Institute at Hawaii Pacific University and Conservation International, which conducted a three-year study to determine the fish production capacity of three separate fish ponds.

“What was good once in the past few hundred years is probably not good in the future,” said Chatham K. Callan, professor in the College of Natural and Computer Sciences at Hawaii Pacific University and director of the Oceanic Institute’s fish research program. “Due to the changing climate and rising sea levels, these ponds need to be reinforced and built to withstand the changing conditions.”

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