10-year battle of sea urchins vs. invasive seaweed

The first hatchery-raised sea urchins outplanted in K膩ne驶ohe Bay are 10-years-old, and the University of Hawai驶i at M膩noa Pacific Cooperative Studies Unit (PCSU) and the State of Hawai驶i Division of Aquatic Resources (DAR) are celebrating the milestone anniversary. The sea urchin hatchery, funded by the National Oceanic and Atmospheric Administration (NOAA) and DAR, successfully transplanted the first cohort in January 2011 and has since released 600,000 sea urchins across the state.
These sea urchins have proven to be incredibly successful at controlling invasive seaweed, a major priority for coral conservation in Hawai驶i. To date, the sea urchin biocontrol project has treated more than 227 acres of reef in K膩ne驶ohe Bay, and has recently expanded to the Waik墨k墨 Marine Life Conservation District to control invasive algae.
Urchins (Tripneustes gratilla) are spawned, settled and raised at the State of Hawai驶i's 膧nuenue Fisheries Research Center at Sand Island as part of a multi-agency effort, involving PCSU, DAR, NOAA, U.S. Fish and Wildlife Service and the State of Hawai驶i Department of Transportation. The sea urchin hatchery鈥攔etrofitted from an old shrimp aquaculture facility鈥攊s a 24/7 operation managed by David Cohen and his staff, who raise sea urchins until their juvenile life stage. It takes approximately four to five months until urchins are large enough to be transferred to K膩ne驶ohe Bay.
Before the urchin hatchery was created, invasive macroalgae (Kappaphycus, Euchuema) would grow in thick mats on top of reefs in K膩ne驶ohe Bay, effectively smothering the reef, blocking sunlight and killing coral. But since these native collector urchins have been outplanted, invasive seaweed cover has been reduced and coral health has improved. Today, these areas are monitored for algae regrowth and urchins are outplanted as needed if invasive seaweed is detected.

"This is one of the most effective marine invasive species control projects implemented in Hawai驶i," said PCSU Director Shaya Honarvar.
"Sea urchins are an incredibly challenging animal to raise in captivity, but under Cohen's leadership the hatchery has been able to produce large numbers of sea urchins consistently, which is a huge accomplishment," said DAR administrator Brian Neilson.
Provided by University of Hawaii at Manoa