⚡ Bar Jacks in Punta Cana: The Reef's Fast Silver Hunters

Hover over almost any reef near Punta Cana for a few minutes and a small group of silver fish will cut past, turn sharply and come back for a second look. That is the bar jack, the most common jack in the West Indies and one of the easiest fish to recognize, thanks to the black and electric-blue stripe that runs along its back and sweeps into its tail.

Bar jacks are not shy, and they are not idle. They are fast daytime hunters with a clever trick: they shadow other animals and steal the prey those animals disturb. Once you know what to look for, you will see them doing it on dive after dive.

Quick Facts

• Name: bar jack, Caranx ruber
• Size: commonly around 40 cm (16 in); the largest recorded reach about 70 cm (28 in)
• Diet: small fish, shrimp and other invertebrates; juveniles feed on plankton near the surface
• Activity: a daytime sight hunter, inactive at night
• Depth: from the surface to about 35 m (115 ft), mostly shallower than about 22 m (72 ft)
• Range: the western Atlantic, from New Jersey and Bermuda through the Gulf of Mexico and the whole Caribbean to southern Brazil
• Status: Least Concern (IUCN)

How to Recognize a Bar Jack

The bar jack has the classic jack shape: a streamlined, slightly flattened, almond-shaped silver body with a deeply forked tail. The field mark is the stripe. A dark band runs along the back below the dorsal fin and curves down into the lower lobe of the tail, and underwater it is usually edged with a bright electric blue. That diagonal swoosh into the lower tail is unique among the jacks you will meet here.

Bar jacks can also change their look. When they feed close to the bottom they may turn noticeably darker or bronze. Juveniles start out with six dark vertical bars that merge into the single back stripe as they grow, and young fish often shelter under floating mats of sargassum.

Look-alikes

• Horse-eye jack (Caranx latus): larger eye, yellow tail, no blue-and-black back stripe; often in big schools in open water.
• Crevalle jack (Caranx hippos): heavier, with a blunt head and a black spot on the edge of the gill cover. Its chest is mostly bare of scales, while the bar jack's is fully scaled.
• Blue runner (Caranx crysos): greenish back, a small dark spot on the gill cover, and no stripe into the tail.

Behavior: The Reef's Opportunist

Bar jacks are sight hunters that chase small fish, shrimp and other invertebrates in mid-water and over sand. Their best-known habit is "shadowing": a bar jack swims tight against a larger animal, just behind or above it, and dashes in when prey bolts. The classic partner is a feeding stingray. As a southern stingray blows into the sand looking for buried crabs and clams, small fish and shrimp scatter, and the jack is waiting. Young bar jacks are especially fond of this trick, and they will also work over other bottom-feeding fish.

They usually travel in small groups, sometimes in larger schools, and occasionally alone. Spawning happens in open water, and the eggs and larvae drift with the plankton before the young settle near the reef.

Where to See Bar Jacks in Punta Cana

Bar jacks are common on almost every reef dive we make. Look up and out rather than into the coral: they patrol the mid-water above the reef top and the edges where reef meets sand. On shallow sites such as El Niño, at about 6 m (20 ft), they often swing past beginner groups and snorkelers. On Rock City, with its canyons and sand channels, watch the sandy floor: wherever a ray is feeding, there is a good chance a bar jack is hanging just above it. Wreck sites are good too, because the baitfish that gather around structure attract hunters.

You will also meet them on our day trips to Catalina and Bayahibe, and you can find the bar jack on our species guide, next to the other fish our guides point out most often.

Photography Tips

• Wait, don't chase. Bar jacks are curious and often loop back for a closer pass. Stay still, keep your fins quiet, and let them come to you.
• Use a fast shutter speed (1/250 s or faster if your camera allows) to freeze a fish that turns in a split second.
• Watch the strobe angle. Silver sides throw back hot spots. Angle your lights slightly outward, or shoot in natural light in shallow water.
• Find a stingray first. A feeding ray with a bar jack riding shotgun is one of the best behavior shots on the reef, and both animals stay busy long enough to frame it.
• Keep your buoyancy steady and stay off the bottom so you don't scare the ray or stir up the sand.

Frequently Asked Questions

Are bar jacks dangerous?

No. Bar jacks pose no threat to divers or snorkelers. They may swim close out of curiosity, but they are only interested in small prey.

Can you eat bar jack?

Yes, it is caught on light tackle and its flesh is rated fair to good. Like other reef predators, though, it can carry ciguatera, a natural toxin that builds up through the food chain, so local knowledge matters before eating any large reef jack.

Why do bar jacks follow stingrays?

To catch the small animals the ray flushes out of the sand. It is a good example of opportunistic feeding, and it does no harm to the ray. For more on the ray's side of the story, read our southern stingray guide.

How big do bar jacks get?

Most adults are around 40 cm (16 in). The largest recorded fish reach about 70 cm (28 in), according to FishBase.

Want to watch them hunt? Join us for a two-tank reef dive in Punta Cana, keep one eye on the blue, and you will soon spot the flash of a bar jack on patrol.