Bar Jacks have a grayish-silver body with prominent golden-brown or blackish line that runs from the snout to the bottom of the tail.  Directly below this dark line is a neon-blue line.   They can reach 15 to 23 inches in length and up to 15 pounds.

Their jaws are filled with numerous slender teeth arranged in narrow bands, and they feed on small fish such as Wrasses, Butterflyfish, Filefish, Blennies, and Gobies as well as shrimp, crabs, squids, worms, and other small seafood. Juveniles feed on smaller food such as plankton and fish larvae.

Bar Jacks heavily rely on the eyesight to find food so they hunt during the day, and generally in large schools.  Their often used for bait, and their natural enemies are mackerels, marlins, dolphins, sea birds and humans. 

Bar Jacks spawn twice each year from March to August in large schools, and and release reproductive cells directly into the water. Females are able to produce 67.00 to 231.000 eggs per season.  Their lifespan is unknown.