Atlantic mackerel are iridescent blue green above with a silvery white underbelly.
Twenty to thirty black bars run across the top half of their body, giving them a distinctive appearance. The efficient spindle shape of their body and their strong tall fin give this fish its ability to move swiftly through the water. Atlantic mackerel have two separate large dorsal fins and, like their relatives the tunas, they possess several dorsal and anal finlets. On average, Atlantic mackerel weigh less than one pound, but individuals of up to two pounds are not unusual. They appear in late spring in many of the state's harbors, coves and coastal rivers where they are sought by eager anglers.