Amberjack are a group of highly sought-after game fish, recognized for their formidable fighting ability and impressive size. These powerful marine predators inhabit various waters globally. Understanding how large these fish can become involves exploring the different species within the amberjack family and the biological and environmental factors influencing their growth.
Amberjack Species and Their Maximum Sizes
The term “amberjack” encompasses several distinct species, each with its own typical size range and maximum potential. Among the most commonly encountered by anglers are the Greater Amberjack, Lesser Amberjack, Almaco Jack, and Banded Rudderfish. The largest of these is the Greater Amberjack (Seriola dumerili), which can reach lengths of nearly 6 feet and weigh up to 200 pounds, though individuals commonly encountered are often around 40 pounds.
The Almaco Jack (Seriola rivoliana) typically averages around 3 feet in length and weighs between 15 and 31 pounds. However, these fish can grow significantly larger, with some records indicating they can reach a maximum length of about 38 inches and weigh up to 136 pounds. Anglers in Florida most commonly encounter Almaco Jacks weighing between 5 and 20 pounds.
The Lesser Amberjack (Seriola fasciata) is a smaller species. Adults typically reach lengths of up to 26.6 inches and can weigh around 10.1 pounds. The Banded Rudderfish (Seriola zonata) is often similar in size to the Lesser Amberjack. They typically range from 12 to 24 inches in length and weigh between 2 and 5 pounds, with a maximum recorded size of 31 inches and 11.7 pounds.
Factors Influencing Amberjack Growth
An amberjack’s ultimate size is shaped by a combination of biological and environmental factors. Age is a primary determinant; Greater Amberjack can live up to 17 years. Females tend to be larger than males at a given age, showcasing sexual dimorphism in growth patterns. Once these fish reach sexual maturity, typically around 3 to 4 years for Greater Amberjack, a portion of their energy is redirected from growth towards reproduction.
Diet and the availability of food sources also play a significant role in how large an amberjack can become. These fish are opportunistic predators. While juveniles primarily feed on plankton and small invertebrates, adults transition to a diet mainly consisting of fish, squid, and crustaceans.
The specific habitat and water temperature further influence growth. Amberjack inhabit offshore reefs, wrecks, and rocky outcrops, often associating with floating debris, which provides both shelter and feeding opportunities, especially for juveniles. Larger fish often prefer deeper waters. Water temperature can impact metabolic rates; for instance, growth in Greater Amberjack can be reduced at temperatures below 21°C and is significantly hindered below 17°C.
Notable Amberjack Records
The impressive sizes that amberjack can attain are well-documented through various fishing records. The current all-tackle world record for a Greater Amberjack stands at 163 pounds 2 ounces (73.9 kg). This specimen was caught by Tadashi Yamanaka in June 2015 off Zenisu, Tokyo, Japan.
An Almaco Jack weighing 136 pounds was caught in Japan in 2020. For the Banded Rudderfish, the all-tackle world record is 5 pounds (2.27 kg), caught in Key West, Florida, in April 2015.
Identifying Large Amberjack
Distinguishing large amberjack species or mature individuals often relies on a combination of body shape, coloration, and fin characteristics. Almaco Jacks generally possess a deeper, more compressed body profile compared to the more slender and elongated forms of Greater, Lesser, and Banded Rudderfish.
Coloration and specific markings also provide clues, though some features can fade with age. Greater Amberjack typically have a distinct dark amber stripe running from their nose to the front of their first dorsal fin. In contrast, Lesser Amberjack feature a dark stripe that extends from the eye but typically does not reach the dorsal fin. Additionally, juvenile Greater Amberjack often display five to six vertical bars along their sides, a pattern that diminishes as they mature.
Fin morphology offers further differentiation. Almaco Jacks are notable for their elongated second dorsal and anal fins, which are proportionally larger than those found on other amberjack species. The Banded Rudderfish can be identified by its comparatively shorter anal fin, which is about half the length of its second dorsal fin and starts further back on the body. For mature Banded Rudderfish, the dark vertical bars present in juveniles typically fade, and they may exhibit white tips on their tails. When a fish is over 3 feet long, it is highly probable that it is a Greater Amberjack, as other species do not commonly reach such sizes.