Gorilla ogo is a fast-growing brittle seaweed that is native to the Indian and Pacific Ocean. It is popular in Asian cuisine and was introduced for aquaculture to Oʻahu in 1974 in Kāneʻohe Bay and Waikiki. This limu was originally used to produce Agar, a jelly-like substance obtained from proteins in the plant and used as a gelatin or thickener. In the wild with no native predators, this ogo flourished and took over reef flats forming thick large mats that kill coral and other native limu. It is considered a pest and invasive species.
Gorilla ogo is a brittle seaweed with cylindrical branches that grows into thick intertwining mats up to 15 cm (3 inches) thick. It turns yellowish in sunny spots and dark green or brownish in shaded areas. It is often used as a crunchy addition to homemade poke or seaweed salad in Hawai’i. It can also be used to fertilize gardens.
Gorilla ogo typically grows in calm, protected waters such as tide pools and reef flats up to a depth of 4 metres (12 feet). It primarily spreads by fragmentation with pieces of seaweed floating to a new location. It doesn’t have a natural predator and so can spread widely covering corals and rocks. It can inhibit new corals from growing and crowds out native seaweeds. It has been introduced as an aquaculture product in many places around the world becoming a common invasive species.
Fishponds are a traditional method of aquaculture used to grow seaweed, shellfish and fish. Hawaiian fishponds are unique because they are built with rock into especially large walled ponds. Harvesters will construct pens to grow juvenile fish and will remove seaweed mats by hand to maintain a healthy pond.