The Greater Amberjack (Seriola dumerili) is a large, fast-swimming fish recognized as a major predator in marine environments across tropical and temperate waters worldwide. These powerful members of the Jack family reach impressive sizes, growing up to 180 cm in length and over 80 kg in weight. Their sheer size and speed necessitate a high-energy diet, making them opportunistic carnivores with a varied menu.
Major Components of the Amberjack Diet
The adult Greater Amberjack’s diet is heavily focused on other fish, a category that often accounts for over half of their total prey intake. They consume a wide range of pelagic (open-water) and demersal (bottom-dwelling) finfish, typically targeting smaller schooling species they can easily engulf. Common prey fish include blue runners, herring, cigar minnows, sardines, and various scads. They also prey on species associated with the structures they inhabit, such as grunts, porgies, and triggerfish.
Cephalopods form another significant portion of the amberjack’s nutrition, with squid being a particularly favored food source. The inclusion of squid provides a high-protein, high-energy component that supports their rapid growth and active lifestyle. These predators will also consume crustaceans and other invertebrates, although these items are generally less frequent in the diet of large adults. Crabs and shrimp are occasionally found in stomach contents, especially when the availability of their preferred fish and cephalopod prey decreases.
Hunting Strategies and Feeding Environment
Amberjack are aggressive and active predators that employ a highly opportunistic feeding strategy. They are often described as structure-oriented hunters, using natural and artificial underwater features as ambush points to intercept passing prey. These structures include rocky reefs, shipwrecks, and offshore oil and gas platforms, which also attract the smaller baitfish they consume. They use their great speed and powerful build to execute sudden, high-energy attacks, overwhelming their prey.
They spend significant time patrolling the water column, from the upper layers to the seabed, depending on where their prey is concentrated. This flexibility allows them to exploit food sources in different depths throughout the day. While they may feed at any time, they are generally most active during periods of lower light, with feeding intensity peaking around dawn and dusk. Their preference for structures and their aggressive nature mean they often strike at anything resembling a distressed or fast-moving baitfish.
Diet Variation Across the Life Cycle
The diet of the Greater Amberjack undergoes a substantial shift as the fish increases in size. This change is driven by their physical growth and their migration to different habitats. Newly hatched and juvenile amberjack inhabit very different environments than adults, often seeking refuge in floating material like sargassum mats or other debris in the open ocean.
In these early life stages, their diet consists of much smaller organisms, including zooplankton, larval fish, and tiny crustaceans. As the fish grows, its mouth size and energy demands increase, making small planktonic items inefficient. Once a juvenile reaches a length of about 20 centimeters, it begins to exhibit more predatory behavior and moves away from the protective floating debris. This transition marks the shift toward consuming larger fish and cephalopods, which characterizes the adult diet in deeper, structured offshore environments.