Seriola rivoliana
Almaco Jack [+]

Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Perciformes
Family: Carangidae
Genus: Seriola
species: rivoliana
+ITIS +WoRMS

Description & Behavior

The Almaco jack, Seriola rivoliana (Valenciennes in Cuvier and Valenciennes, 1833), is a dusky-colored amberjack with a faint amber or olive stripe running down its side. The body and lower fins are generally dark brown or dark blueish green, and the lighter-colored belly may look brassy or even lavender. The Almaco jack's dorsal and anal fins are high and elongated, with deeply sickle-shaped outer edges. The nuchal bar in adults is dark-colored, as are the fins, excepting the pelvic fins, which are white on the ventral side. Almaco jacks typically have less elongated, more flattened bodies than other species of jacks (140 species of jack have been identified to date). Their dorsal fins also distinguish them from other jacks—the first few rays of the soft part of the dorsal fin are more than twice as long as the dorsal spines in Almaco jacks, whereas in other species the rays are less than twice the length of the dorsal spines. Adults can reach 1.6 m and usually weigh 6.8-14 kg, though they may exceed 59 kg. Almaco jacks are known for their stamina and strength, making them a prized target of deep-sea sport fishermen. Like other jacks, Almaco jacks like to remove parasites from their skin by rubbing themselves on the rough skin of passing sharks—and occasionally, human divers they mistake for sharks.

World Range & Habitat

The Almaco jack, Seriola rivoliana, is a wide-ranging pelagic species that usually lives in small groups on outer reef slopes or offshore banks 160 m out to sea, at a depth ranging from 5-160 m. Adults are largely nomadic. Almaco jacks are more oceanic than most other species of jacks, though they do tend to frequent rocks, wrecks and offshore oil and gas platforms. The species inhabits both tropical and subtropical waters. In the Indian Ocean and West Pacific, the Almaco jack can be found off the coast of Africa from Kenya to South Africa. The species has also been spotted off the Mariana, Wake, Ryuku, and Kermadee Islands, as well as New Caledonia. In the Eastern Pacific, the Almaco jack covers an area stretching from southern California to Peru, including the Galápagos Islands. The species can also be found in the Atlantic, particularly from Cape Cod in the United States to northern Argentina, though it is rarely seen north of the Carolinas. Its presence has not been fully documented in the eastern Atlantic, though some Almaco jacks have been seen at Lampedusa Island in the Mediterranean and, rarely, off the coast of England. Young Almaco jacks sometimes live in the branching algae beds known as Sargassum or around other floating objects.

» GBIF occurrence data in Google Earth [Tips] | Ocean Biogeographic Information System (OBIS) (World Distribution) [about]

Feeding Behavior (Ecology)

The Almaco jack, Seriola rivoliana, is a fast-swimming predator that feeds both day and night. It eats mainly fishes, particularly baitfish, but also eats invertebrates such as small squid.

Life History

Little is known about the reproductive habits of the Almaco jack, though scientists expect that its behavior is similar to that of the greater amberjack. Spawning occurs offshore at various times throughout the spring, summer and fall, depending on latitude and water temperature. The minimum population doubling time is estimated to be 4.5 to 14 years.