Meet roi the Peacock Grouper

If you have dove anywhere in warm tropical waters you more then likely have seen the large grouper species that are quite common in French Polynesia, Micronesia, Indonesia and the Caribbean. Many of the grouper species grow over three foot long and can get up to 300 pounds or more! The grouper are one of the top predator species in tropical seas and they are also a valuable food source for local communities!

But this is not the case here in Hawaii. Native Hawaiian grouper are extremely rare and only seen from time to time in the far Northwest Hawaiian Islands. But we have an imported grouper species all throughout the main Hawaiian islands called the roi or peacock Grouper. This fish was imported to Hawaii in the 1950s from French Polynesia and since then has spread to almost all of the Hawaiian coral reefs.

Since the roi is a grouper it is a super good fish to eat. Where it occurs naturally in Tahiti it sells for up to $8 a pound and is a prize dish in the local restaurants. Even though this 20-inch long fish is now very common in Hawaiian waters and easy to catch it is not often eaten by the local community.

This is a problem because the roi are eating up many of our local fish species! Hawaiian reef fish did not evolve with any large predator groupers so they do not recognize the roi as a threat like they would a large ulua. I have watched reef fish just swim right up to the roi and look at it like they do not even know it is a fish.

Then the roi just gulps it down with its large mouth and series of hundreds of small bristle like teeth. The roi in Hawaii has it made and their numbers have swelled in recent years to the point they are seriously damaging our coral coral reef ecosystem.

In one, year long project I personally speared over 250 roi just in Hanalei Bay and lots of other local divers spear the roi often to try and control their numbers. We figured that one roi will eat over 200 local reef fish in its lifetime so by spearing one roi you are saving a lot of our native fish!

Why don’t more people eat the roi here in Hawaii? Great question and some misleading information may be the answer. Some of the people who have eaten the roi have got sick and they felt it was due to a fish toxin the roi may carry in its flesh called ciguatera.

This fish toxin can make you sick and it is naturally occurring but some fish species tend to have higher concentrations then others. In order to find out if the roi is truly toxic to eat we did a massive fish toxin testing project with the University of Hawaii where we tested over 3,000 roi for ciguatera. The results were mixed. On some Hawaiian Islands the roi had ciguatera and on others like Kauai the roi had very little ciguatera!

Since there is no proven method for testing for ciguatera that is inexpensive, and this neurotixin does not break down when you cook the fish we have developed a simple test to see if the fish you catch is clean.

I often eat invasive reef fish because that helps the entire coral reef ecosystem but I simply eat a small dime size piece of the fish after I catch it. If it contains ciguatera you would have some kind of mild stomach reaction within three to five hours according to the finding from the UH study.

If I had any kind of reaction I would not eat the rest of the fish, but after testing hundreds of roi this way I have never had a bad fish from Kauai!

Catching the roi for food is a good sustainable food source that helps our coral reefs and maybe we can lower the populations to help our native fish species, but each person who chooses to eat them really needs to be cautious and not eat a large portion of the fish right way until you know it is safe.

What we are hoping for is to develop a safe, proven, inexpensive test kit to do positive test for ciguatera right at the beach but so far no such kit has been developed to my knowledge.

The roi are extremely beautiful fish to look at and they may or may not have white bands on their blue and brown smooth skin. The roi can change colors quickly and be solid brown with blue dots or brown with bright white stripes.

You can see the roi in action in my video The Worlds Guide to Hawaiian Reef Fish up on my underwater educational web page at www.underwater2web.com and also follow my marine life identification series on my Instagram at terry.lilley.

Aloha from under the surf,

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Terry Lilley, Marine Biologist, Hanalei, underwater2web.com, www.gofundme.com/5urrm4zw, All Photographs © 2016 Terry Lilly