The Hawaiian grouper was first formally described in 1901 as Epinephelus quernus by the American ichthyologist Alvin Seale (1871-1958) with the type locality given as Honolulu.^[3] It was formerly considered to be in the genus Epinephelus but is now considered to belong to the genus Hyporthodus.^[4] The specific name quernus means "oaken", presumably a reference to its reddish colour as an adult.^[5]

The Hawaiian grouper has a body which has a standard length that is 2.3 to 2.7 times its depth. It has an angular preopercle which has 3-4 enlarged serrations at its angle, with the lowest pointing downwards. The upper margin of the gill cover is convex.^[6] The dorsal fin contains 11 spines and 14-15 soft rays while the anal fin has 3 spines and 9 soft rays.^[2] The membranes between the dorsal fin spines are deeply notched. The caudal fin is rounded. The adults are dark brown in overall colour and are marked with 8 vertical series of faint white spots which are obscured by many extra pale spots and blotches which vary in size. The fins of adults are largely plain and have a similar colour to the body apart from a small number of pale spots along the base part of the dorsal fin. Depending on habitat and where geographically found, some have a slight blue tint to their belly in the mature older adults, whereas in other areas they can have a slight reddish tint possibly for camouflage from predators.^{[citation needed]} Juveniles are more variable in colour and may be pale greyish and the series of pale spots are more distinct and unobscured.^[6] This species has a maximum published total length of 122 centimetres (48 in) and a maximum weight of 22.7 kilograms (50 lb).^[2] The largest recorded specimen caught was 31.75 kilograms (70 lbs) off of Puako, Northwest Hawaii Island.^{[citation needed]}

The Hawaiian grouper is endemic to Hawaii and its range includes the Northwestern Hawaiian Islands and the Johnston Atoll.^[1]

The Hawaiian grouper is a demersal species which is found on coral and rocky reefs at depths between 20 and 380 metres (66 and 1,247 ft). It is a protogynous hermaphrodite and 50% of the females are sexually mature at 58 centimetres (23 in), when they are around 6 years old, although it has been recorded in fish at 32.8 centimetres (12.9 in). At a total length of 89.5 centimetres (35.2 in) 50% of the females change sex to become males, although this can occur at 75.3 centimetres (29.6 in). The spawning season runs from February to June, peaking in March.^[1] This predatory species prefers to prey on other fishes with crustaceans, especially shrimp, as a second preference.^[6]

The Hawaiian grouper is valued for having clear white flesh which has a delicate flavour.^[7] It is regarded as a member of the "Deep 7" group of fish species which live in deep water, near the bottom, and are a valuable resource for fisheries in Hawaii, these species accounting for 50% of the total commercial catch in the State.^[8]

• Pacific Islands Fisheries Science Center Administrative Report H-08-06, 19 p, http://www.pifsc.noaa.gov
• Gillgren, Jerry G.; Ballam, Anthony: Malama Charters Hilo LLC, Commercial fishing vessel "Jovan Lee" field work, Northeastern coast of Hawaii Island (12/2019-3/2020)