Fishpond aquaculture is a practice that exists all over the world, from Europe to North America to East Asia. While practices vary by location depending on the landscape and geography of each region, Hawaiian aquaculture is especially unique and has been used since the first Polynesians made their way to the islands. Fish remains a vital source of protein in the diets of islanders, and fishing success is largely dependent upon weather and ocean conditions. Aquaculture acts somewhat as an insurance policy, guaranteeing that protein will be readily available when needed, even if conditions are not favorable for fishing.
Fishpond aquaculture is different from the aquaculture we typically think about because it relies on the natural structures that are already present in the environment, rather than farming fish in a man-made system. A wall is built on a shallow reef flat circling the mouth of a freshwater stream or river as it reaches the ocean. Constructed from coral, lava, and other semi-porous materials, the water contained within the wall remains uniform with the water level of the ocean, as it is allowed to ebb and flow with the tide. Sluice gates formed from sticks and branches are the crucial components that allow the fishpond to be successful.
The gate is just the right size to keep large fish and predators out but allows young fish to get in. The protected brackish water creates an ideal, safe site for the fish to grow up, and once they reach a certain size, they are unable to leave and are eventually harvested. Herbivorous species are targeted because they are easy to feed and grow quickly compared to their carnivorous counterparts. Mullet and milkfish are a few of the most common species found in Hawaiian fishponds.
What makes Hawaiian fishponds different from other fishponds is that limu (algae) is cultivated to guarantee an abundant supply of food for the fish to maximize their growth. Similar to a rancher caring for the grass in the pastures, the cultivation of algae allows herbivorous fish to grow without being fed and attracts young fish to the pond so it is restocked naturally.
During my time in Hawaii, I had the chance to volunteer with the restoration of an ancient fishpond on the East side of Oahu, where we worked to extend the fishpond wall, and remove invasive mangroves. It was a lot of work, but with a devoted and enthusiastic team, we were able to accomplish a lot. The project was a lot of fun, and it was extremely rewarding to be able to see all the progress we made.