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Removing Roi

A No Brainer or Not? 

"“People can say they know, but without the research, we won’t have proof to show what is happening.” 

Kawika Auld
Hawai'i Island fisherman

What if you could get paid to go fishing? Four Hawai‘i Island fishermen did. Hired to help with a research project along the South Kohala coastline, the fishermen joined The Nature Conservancy and a team of University of Hawai‘i marine scientists to measure the effect of removing introduced peacock grouper (Cephalopholis argus), or roi, from a Big Island reef.

Roi eat native fish, lots of them. So if you remove roi, you help native fish, right?

That’s been the premise behind recent fishing tournaments called “roi round-ups”, in which Hawai‘i spear fishers win prizes for removing invasive fish. But the reality is, we don’t really know what effect roi have on native fish populations. It’s important for scientists to measure the effects of roi removal so managers can act – or not.

If roi removal is demonstrated to help native reefs, managers could take additional steps to remove them, including hiring local fishers to do the job. This information will also help inform reef management across the state.

“People can say they know, but without the research, we won’t have proof to show what is happening,” said Kawika Auld, one of the four fishermen assisting with the project.

Funded by the National Oceanic and Atmospheric Administration (NOAA), the Michael Morriss Memorial Fund and the Hawai‘i Coral Reef Initiative, the Nature Conservancy’s project on Hawaii Island is designed to answer three questions:

• Is it possible to completely remove roi from a reef, and if so, what level of effort does it take to get them all?

• Do roi recolonize an area, and if they do, where do they travel from?

• Does the reef improve after the roi are removed, and are the changes lasting?

Over the past year, the team established the baseline, or current status, of roi so there is a comparison against which to measure changes in roi populations over time. They also established the baseline for the reef and fish community in the project area, so there is a comparison against which to measure changes in these communities over time.

In addition, the team tagged and released roi outside the project area to determine if these fish would recolonize the area where roi are removed. Finally, they removed roi from the project area.

“We are now monitoring the area, and will continue to do so over the next several years to observe how native fish, coral, algae and other creatures respond to the roi removal, and to determine if and when roi return to the reef,” said Chad Wiggens, Hawai‘i Island marine coordinator for the Conservancy.

It will take time to observe the changes in the reef, the fish and other creatures, but researchers and fisherman hope the project will result in useful information that contributes to positive efforts to protect Hawai‘i reefs.

“I’m not a marine biologist,” said Auld. “I’m just a fisherman who loves the ocean. If this project can generate enough information to create jobs, that would be great. But if not, we have a better understanding of how this invasive species affects our reefs.”
 

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