They come from the Indo-Pacific which is variously a commercial game fish, an invasive species, and occasionally an aquarium resident. Its species name comes from its resemblance to the “a hundred staring eyes” of the monster Argus in Greek mythology.
Larger specimens sometimes develop four to six lighter vertical bars on the back half of its body. Cephalopods Argus, Vilamendhoo Maldives 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.
It makes use of a variety of habitats but prefers the exposed fronts of reefs, at depths of up to 40 m. Hunting, they lie on the bottom and surge forward, preferring juvenile surgeon fish and crustaceans.
This grouper may follow and cooperate with another predator species, such as an octopus or eel or camouflage themselves in a school of surgeon fish. Multiple individuals may cooperate to harass an eel to get it to flush prey for them.
The species typically sit on a coral head, retreating when startled. Red Sea males defend harems of 2–6 females in territories ranging up to .5 acres (0.20 ha).
The male visits each female daily, raising his dorsal fin to signal his approach. The females emerge from hiding, erecting her own dorsal fin and changing to a lighter color.
Territorial disputes may involve “color fights” in which two males positioning themselves at right angles to each other. They then darken their color and repeatedly switch their bars from dark to light.
During courtship, both sexes darken except for a white keyhole-shaped patch at the center of the body. As a predator it will eat any smaller aquarium inhabitants such as dam selfish.
Known in Hawaii as ROI, the state introduced the species in the 1950s to enhance local fisheries. Hawaii's Division of Aquatic Resources (DAR) finds that ROI have become the reefs' dominant predator.
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. 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. Because of the toxicity issues, ROI does not have a functional fishery, with just an average of $1000 per year in sales.
Roi's feed primarily on juvenile fish that have recruited the reef. The family of fish that make up the majority of their diet Scarsdale or Parrot fish, are crucial to the coral reef ecosystem by removing algal growth on coral colonies through feeding.
Hawaii has the highest rate of endemic of its nearshore marine fish species at 24.3%. 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.
On Maui, spearfishes 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.
Groupers are solitary carnivores that hunt near the bottom usually at dusk. Juvenile fish become adults and some change shape or their color.
Click the image(s) to explore further or hover over to get a better view! This fish is an attack predator with a number of hunting techniques: lying to wait in coral, swimming in mid water, following other predators like eels and octopus and catching their prey if originally missed, and hiding within schools of fish and darting out at unsuspecting prey.
Habitat: C. Argus can be found on shallow exposed reefs in warm tropical waters. It is a protogynous hermaphrodite, meaning it begins life as a female and changes to a male as it matures.
It is treatable in humans, but the concern is that ciguatoxin can move up the food chain via bio amplification and spread to other species. As can be seemed in the images they can also put light whitish vertical bars on the body which aids with camouflage and is used for territorial disputes and mating.
In research conducted on the Great Barrier Reef individuals of up to 40 years in age were found. They have the ability to lighten their coloration and will sometimes have white vertical bars down their body.
The two males approach each other from the front and then turn sideways at close to a right angle so that each can see the others body. They are found on the East coast of Africa from Durban in the south to the Red Sea, eastwards to the mid Pacific including most islands.
They are typically found on exposed reefs rather than in protected areas or estuaries. However, multiple cases of ciguatera poisoning occurred which were traced back to the PeacockGrouper.
Their main diet is small fishes and crustaceans, however given they are caught by fishermen on the hook this indicates that they will scavenge as well. They are ambush predators and feed in the early morning and late afternoon when their coloration gives them more camouflage.
Based on social and environmental cues some larger females will turn into males. Mating typically occurs around spring tides when there is more water movement.
With their bright coloration these fish are kept in large aquariums by some specialized collectors but because of their propensity to eat smaller fish great care has to be taken with their tank mates. If one dives in the Marine Park on Mafia Island there are noticeably far greater numbers of this species.