He'eia Fishpond

(c) Michael Walters via Flickr

By the 14th century, fishponds were common in Hawai’i and other Pacific Islands, and were an important source of food for ancient Hawai’ians. They were created by ali’i (chiefs) to feed people when the surf made it too dangerous to fish in deeper water. The exact date of He’eia fishpond’s construction is unknown, but it was built at least 600 years ago by the residents of the He’eia ahupua’a, the slice of land that runs from the mountains down to the ocean and includes He’eia stream and crop land.

He’eia fishpond is an 88-acre fishpond located in Kane’ohe Bay on O’ahu. Its structure consists of a porous stone wall surrounding a natural bay, so it’s bound on one side by land and on the other by the manmade wall. Fresh water flows into the pond via He’eia stream, and ocean water seeps in through cracks in the sea wall and flows in through gates in the wall, called makaha. This design allows small fish and larvae to enter the pond (via the makaha or cracks in the rocks) and grow in the relatively protected, estuarine environment, but it also prevents them from leaving until the makaha are opened. Ancient Hawai’ians fished inside the pond walls and also at the makaha. This low-impact aquaculture fed thecitizens of the ahupua’a.

Benthic habitat in the pond is laden with silt and the water contains a lot of sediment. In the background is the alien crab Thalamita crenata.

The structure of the fishpond has been disrupted by storm events and periods of disuse, so the pond currently has more breaks in the sea wall than it had originally. It also holds more sediment, because runoff from He’eia stream has increased as a result of upstream construction. Additionally, the pond has endured an invasion of red and white mangroves (neither of which are native to Hawai’i) and has also been invaded by three species of invasive macroalgae since 1970 (here is a video about Gracilaria salicornia, or gorilla ogo). These algae have stiff fronds that create a bushy canopy above the sediment. These physical changes and biological invasions have changed the fishpond environment, but it still sustains a diverse invertebrate and fish community. The stewardship organization for the fishpond, Paepae o He’eia, is actively restoring the original fishpond structure, managing the current fish populations, and educating the community so that the fishpond can be a productive fishery again.

 Seawater flowing from Kane’ohe Bay through the sea wall. This portion of wall is made of volcanic rock.