The humpback grouper, Cromileptes altivelis, is a distinctive marine fish found throughout the tropical waters of the central Indo-West Pacific region. It inhabits clear waters around lagoons and seaward reefs. This species belongs to the family Serranidae, which includes sea basses and anthias, and plays a role in its reef ecosystems.
Identifying the Humpback Grouper
The humpback grouper is a medium-sized fish, typically growing up to 70 centimeters (28 inches) in length, though some individuals may reach slightly larger sizes. Its body is laterally compressed and relatively high. A prominent feature is the sharp rise at its nape, giving it a characteristic humpbacked appearance.
The head is depressed anteriorly and elevated posteriorly, further accentuating this unusual shape. Young humpback groupers display a white background with round black spots and often swim with their heads pointed downwards. As they mature, their coloration shifts to grey and beige with darker blotches across the body, still covered in small black spots.
Life in the Reefs
The humpback grouper inhabits clear waters, favoring environments such as lagoons, outer reef slopes, and seaward reefs. They often seek shelter near caves, ledges, or areas with dead or silty substrates. These fish are found at depths ranging from 2 to 40 meters.
As a predatory fish, the humpback grouper’s diet consists of smaller fish and various crustaceans, including shrimp, krill, squids, and clams. They are ambush predators, often lying in wait for prey. Their feeding activity is most pronounced during sunrise and sunset.
Humpback groupers are demersal, meaning they live on or near the seabed, and are largely solitary, defending their territories. Despite their solitary nature, they have been observed swimming in pairs or small groups. This species exhibits protogynous hermaphroditism, a reproductive strategy where all individuals are born female and can transition into males later in life.
Female humpback groupers can begin this sex change, with individuals becoming male. This transformation occurs in dominant, mature females when there is no dominant male present. Spawning activity for the humpback grouper peaks between October and January. During courtship, individuals engage in a ritual of swimming in circles, and fertilization occurs in open water, producing pelagic eggs that drift with ocean currents.
Conservation Concerns
The humpback grouper is currently classified as “Vulnerable” on the IUCN Red List of Threatened Species. This designation reflects concerns over its naturally low population density and susceptibility to various human-induced pressures. Overfishing is a threat, particularly for the live reef fish trade, where its high market value in regions like Southeast Asia leads to intense exploitation.
Habitat degradation also poses a risk to the species. Coral bleaching events, exacerbated by rising ocean temperatures, destroy the reef structures that humpback groupers rely upon for shelter and foraging. Destructive fishing practices, such as the use of explosives or cyanide, further damage these fragile ecosystems, directly impacting the grouper’s survival.
Climate change contributes to these issues by increasing ocean temperatures and causing ocean acidification, further stressing coral reefs. While aquaculture efforts exist for this species, there is no evidence that captive breeding has reduced fishing pressure on wild populations. Conservation strategies include implementing size limits, establishing no-take zones, and enhancing efforts to control fishing activities.