[3] The species is extremely widely distributed, occurring in warm waters from the Red Sea to South Africa and east to French Polynesia and the Pitcairn group.

[3] This grouper may follow and cooperate with another predator species, such as an octopus or eel or camouflage themselves in a school of surgeonfish.

Hawaii's Division of Aquatic Resources (DAR) finds that roi have become the reefs' dominant predator.

[4] Prized as delicious eating in other Pacific regions, in Hawaii's waters roi may contain the ciguatera toxin, which builds up in humans and causes serious illness.

[4] A study published in 2007 found that 18% of Roi sampled from Oahu and Hawaii islands had toxins above levels safe for consumption.

Due to high variability of toxin levels between individuals in the same area, toxicity cannot be predicted based on location.

[5] Analysis of stomach contents of Hawaiian roi found that diets consist of 97.7% fish and 2.3% crustaceans.

[5] Of the fish eaten, there were 27.1% Scaridae (Parrotfish), 18.7% Acanthuridae (Surgeonfish), 17.6% Squirrelfish, 13.7% Monacanthidae (Filefish), 9.3% Priacanthidae (Bigeyes), 4.3% Chaetodontidae (Butterflyfish), 2.8% Aulostomidae (Trumpetfishes), and 6.9% other consisting of 9 families.

[5] The lack of natural predators to control Roi populations along with their high efficiency is a major threat to the unique fish fauna found in Hawaii.

[5] On Maui, spearfishers participate in "Roi Roundup" tournaments that target these problematic fish, attempting to reduce their numbers and impact.

This practice has spread to other islands, where there are similar tournaments that target roi and other invasive fish species.