DLNR Press Release: LIMU’S LOVING HUMANS ARE NOT THE ONLY ONE TO ENTER “THE YEAR OF LIMU”
Published on 5 Apr 2022 in Latest news from the department, Press room
(HONOLULU) – As limu enthusiasts across Hawai’i celebrate 2022 as “the year of the Limu,” as Governor David Ige proclaimed, small sea urchins growing in tanks at the DLNR Anuenue peaches on Sand Island, nibble on hatchery- cultured seaweed.
“It’s certainly ironic that we’re feeding sea urchins a native species of limu to make them big enough to go out in the field to eat invasive algae,” explained David Cohen, sea urchin hatchery manager at the Division of Aquatic Resources (DAR) of the DLNR.
For more than a decade, sea urchins have been bred at the hatchery for possible planting in Kāne’ohe Bay or off Waikīkī. They are collector sea urchins and their mission in life is to devour the invasive algae that smother the coral colonies. Hatchery workers expect to reach the milestone of one million sea urchins planted by the end of the year.
Cohen said: “When we set up the sea urchin hatchery, we started targeting two invasive algae found in Kāne’ohe Bay. We didn’t want to grow non-native or invasive algae because we were concerned that we would end up proliferating invasive algae in the marine environment. So they are only fed native limu until they are big enough to go out in the field and start eating invasive algae.
When the sea urchins are between 5 and 15 millimeters…about the size of a pencil eraser…they are big enough to start eating algae. During this two to three month period, native seaweed is their main source of nutrition. They are released when they are about the size of a penny. “Limu has a variety of beneficial uses. For us, the main purpose of the limu is to feed it to the urchins until they are big enough to go out in the field,” Cohen added.
Limu is a primary food source for people in Hawai’i, across the Pacific, and around the world.
The hatchery team cultivates a beautiful seaweed, commonly known as red sea lettuce or lepe-o-hina in Hawaiian. It’s a fast-growing native limu, but for some reason sea urchins don’t really like to eat it. Cohen remarked, “It’s kind of a double-edged sword. It grows well and looks great. However, it is not a good food for sea urchins. We use it more for planting purposes and maybe for people to eat.
Every day, hatchery technicians closely monitor the sea urchins in dozens of long tanks. At mealtime, they clean the limu with a fresh water rinse, break it up and place it in the sea urchin tanks.
“He’s a native limu and the kids love him. In the wild, they eat anything, and a graduate student’s work shows that collector sea urchins prefer invasive algae. In our hatchery, they grow up as limu connoisseurs, feeding on the finest native algae. Once they’re in the ocean, they become fast food consumers,” Cohen joked.
Since the beginning of the project, sea urchin collectors have been credited with vast improvements to the many coral colonies in Kāne’ohe Bay.
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(All images/videos courtesy of DLNR)
HD video – Limu for sea urchins who love seaweed web functionality:
HD video – Limu and sea urchins at the Anuenue Fisheries Research Center (February 25, 2022):
(shoot sheet attached)
Photographs – Limu and sea urchins at the Anuenue Fisheries Research Center (February 25, 2022):
Senior Communications Manager
Hawaii Department of Lands and Natural Resources