State helps sea urchins reproduce to combat invasive algae

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They’re considered the goats and gardeners of the ocean — sea urchins that love the taste of an invasive algae that is smothering Hawaii’s reefs.

The Super Sucker made its debut at Kaneohe Bay in 2006 and has been a great tool in the fight against an invasive algae. But it can only do so much. The real hero in this war could be the Native Hawaiian Collector Urchin.

“They can remove the seaweed, but the seaweed will grow back. These little sea urchins are our gardeners. They’re our little goats. They’ll stay out there and nibble away on the seaweed and keep it all down for us,” invasive species biocontrol specialist David Cohen said.

But these nibblers are having a tough time keeping up.

“Okay, so we’ve got a male going here,” Cohen said.

That’s where this team from the Division of Aquatic Resources is stepping in.

“We know from the color and consistency that this is sperm and not eggs. In a few minutes, hopefully we’ll see some eggs and then we’ll see the difference,” Cohen said.

A dive team gathered about a dozen sea urchins Monday morning and brought them to the Anuenue Fisheries Research Center at Sand Island for spawning.

“So earlier, you asked me Ron how I could tell the difference. This is more of an orange color,” Cohen said.

In this environment, a female can release a few million eggs. Once the eggs and sperm are collected, they’re taken to a hatchery where they’re fertilized.

“After about 24 hours, the eggs will develop into free-swimming sea urchin larvae,” Cohen said.

Eventually, they’ll stop swimming and settle down to become baby sea urchins.

“These sea urchins are about 3 months old,” Cohen said.

They’ve grown to about 10 millimeters.

“These guys are growing in here and we feed them on cultured seaweed and when they’re about five months of age, they’re big enough to go out into Kaneohe Bay and start eating that invasive seaweed,” Cohen said.

These sea urchins are about the size of a nickel. They’ll be released on Thursday to join the fight.

“They’re out there on the reef doing a really important job. They’re out there eating that invasive seaweed and helping to restore the coral reefs at Kaneohe Bay. There’s only so much the Super Sucker can do right? There’s only so much the Super Sucker can do,” Cohen said.

And it all starts at Sand Island.

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