Roi, Hawaii’s Most Dangerous Fish

Roi or peacock grouper, were introduced into Hawaii in 1956 from Mo'orea to add to the food source for Hawaiian fishermen. This fish grows to about 16 inches and five pounds and they are now very common in Kaua'i. This fish fills a nitch that no other Hawaiian fish fills and it eats a wide variety of reef fish. Roi spend most of their time in deep caves and cracks in the reef where they prey on other fish like aweoweo, mempachi and ala'ihi. These red cave fish are active at night and sleep in the caves during the day. Since roi did not evolve in Kaua'i these cave fish do not recognize roi as a predator. These fish will swim right up to a roi to be eaten. Ulua and puhi will also eat these cave fish, but the cave fish recognize them as predators and have learned to avoid being eaten most of the time.

Roi know every cave and crack in the reef. I am a marine biologist and I have over 3,000 scuba dives, many of which were observing the roi's behaviour. I shoot HD video of roi and other marine life and have over 1,000 of underwater video from Kaua'i. I also make movies for schools, government agencies and the public about our marine life and invasive species like roi, ta'ape and to'au. I am currently doing a ciguatera research project with Paul Bienfang at UH where I send him roi for research and testing. My research has been funded by myself.

I have video of many roi on the north shore of Kaua'i and I see an average of 14 roi on each, one hour scuba dive. These roi live from 5 feet deep to 80 feet deep and they move freely about the reef. I have followed many roi that travel 30 to 40 yards across a reef ducking into each cave and coming out of a different cave many yards away. They know each lava tube and large roi live in the same area as young roi. I have observed several large roi that seem to stay near the same caves but they will move when the surf changes or you scare them away. They do not seem to be very territorial and after taking video of over 500 roi in Hanalei Bay I have not observed roi fighting each other.

In Hanalei Bay from the shore out to one mile I have done over 100 kayak scuba dives and I have speared over 80 roi of which I sent to UH for testing. Even though I have taken a lot of roi off the reef I still see 10 to 15 on each dive! I mount my spear gun onto my HD video camera and I take video of each roi before I spear it so I can document its behaviour, what fish are in the area and get a GPS, date and time on each take. I also free dive to spear roi and I often see 20 roi or more in a two hour dive. Many times I see more roi, ta'ape and to'au on one dive than I see native fish and on my blog at I have a short movie post about roi, that shows their concentration on the reef and how I take them for testing.

There are thousands of roi in Hanalei Bay! I have seen and taken video of roi all over Kaua'i and Hawaii and see the same thing in many places. This concentration of roi vs native fish is very dangerous for the long term health of our reefs. Ten years ago at many spots on the north shore like Tunnels Reef, I have seen many of the native fish decline and the roi spread. Back then I could easily spear 5 to 10 aweoweo in one hour and saw one or two roi. Now I see almost no aweoweo and 5 to 15 roi on each dive!

Fishermen do not normally eat the roi because they have been known to carry the ciguatera toxin and they could make you very sick! We are not yet sure what percent of the roi carry the toxin but I have sent over 300 roi to UH for testing and we should soon have some figures. The current test kit for ciguatera is not extremely accurate and cost a lot. If UH could make a good test kit that cost little then fishermen could go back to catching and eating roi. This would be very good!

Currently free divers spear roi on a regular basis. This helps control the population explosion but it is not enough. We need 5 or more free divers at each reef spearing roi on a regular basis. Free divers can target certain species without damaging the reef or marine life. I have video of many turtles and sharks with fish hooks and line dangling from their mouths, but free divers do not have this to worry about.

If each free diver would catch 3 roi on a dive he would save hundreds of reef fish from being eaten! Roi can eat 50 fish or more a year and can live for 10 years. This is a lot of reef fish they will eat! If a diver took three roi a dive and then two fish for his food, then he would be adding native fish to the reef in the long run. If we could offer a bounty for roi of $10 per fish then free divers could spend a lot of time taking roi and balancing out the predator prey relationship!

Some scientist claim that roi take the place of Ulua as a top predator. I feel this is not true as roi live and feed differently than Ulua. Roi did not evolve on Hawaiian reefs and they should not have been released and they should be removed! If we would spend more time and money studying Ulua, Uku, Omilu and other predators and develop additional plans to increase their populations, then we would be returning our reefs to a healthy state. Using an invasive species to repair a damaged ecosystem rarely if every works!Roi could also carry bacteria that are not native to Hawaiian waters.

I dive or surf every day and I have been spear fishing for 40 years. I catch my own food and am healthy because of that. I also take a lot of roi off the reef to help save thousands of reef fish. I know many local spear fishermen that do the same and I think their efforts are helping our reefs in Kaua'i. I did an underwater movie about Kauai's free divers and they are very good at what they do and they understand the ocean and marine life quite well.

Rising sea levels, run off, improper building, polluted rivers and over use of certain reefs by tourist cause much more damage to our coastal ecosystem than fishermen do. I have movies of all of these negative events to share. Fishermen help with fish information, tagging and removing target species and it will be the fishermen that help protect our reefs for future generations to enjoy, as they have for hundreds of years in Hawaii.

I have over 500 hours of roi research, video and finished movies to share with others who care about the future of our reefs, and my ongoing educational blog is being used in schools all over Hawaii to educate our children. As scientist we need to work with fishermen, divers, surfers, hunters and other native people as they are "the eyes on the reef" we need to learn from and share with. We do not have time to fight over regulations as the sea is changing quickly, and we all need to join together and share our knowledge and efforts.


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