Latin name

Caranx hippos; Caranx caninus

Other names

Сommon jack, crevally, toro, trevally, horse crevalle; Spanish: cavallo, chumbo, cocinero, jurel común. Toro, crevally, cavalla, jiguagua; Spanish: aurel, burel, canche jurel, chumbo, cocinero, jurel toro, jurelito, sargentillo.

Identification

Both species are bluish-green or greenish gold on the back and silvery or yellowish on the belly. They are compressed, their deep body has a high rounded profile, and a large mouth. The tail and anal fin may be yellowish, and the dorsal fin ends and upper part of the tail are sometimes black. There is a prominent black spot on the gill cover and another at the base of each pectoral fin. The soft dorsal and anal fins are almost identical in size. Externally, the two species differ from each other only in the presence of a larger maximum number of scales, up to 42 in the Pacific Crevalle Jack, compared to 26-35 in the Crevalle Jack.

Distribution

In the western Atlantic Ocean, crevalle jacks are found from Nova Scotia south to the northern Gulf of Mexico. In the eastern Pacific, they are found from San Diego, California, to Peru.

Habitat

Both species can tolerate a wide range of salinity and often inhabit coastal areas with brackish water, and may also move up rivers, often visiting coastal reefs, harbors, and sheltered bays. Small fish are sometimes found on the sandy and muddy bottoms of very shallow bodies of water, as in estuaries and rivers. They are common in depths up to 130 feet and often move to cooler and deeper waters in the summer. Keeps most frequently in small flocks near shores.

Size

With an average weight of 3 to 5 pounds and a length of 1 to 21⁄2 feet, crevalle jack can reach 10 pounds. Pacific crevalle jack are usually smaller. The world record for crevalle jack is an Angolan fish weighing 58 pounds and for Pacific crevalle jack is a Costa Rican fish weighing 39 pounds.

Life history and Behavior

Spawning takes place in the sea from March to September. Young fish gather in small or large, fast-moving schools. Larger fish are often kept singly.

Food and feeding habits

Voracious predators, feeding on shrimp, other invertebrates and small fish. Often corner a cluster of bait fish near the surface and feed or chase their prey on beaches and offshore jetties. Fish of both species usually grunt or squawk when caught.

Reproduction

Reproduction of the crevalle jack is a process adapted to the conditions of warm tropical waters, with some interesting features. They spawn during the warm season. In Florida waters, this period lasts from March to September, and in southern Florida, the peak of activity occurs in spring and early summer. The process usually takes place in the open sea. However, spawning has also been recorded on coastal reefs and in bays, for example, off the coasts of Belize and Colombia. Before spawning, crevalle jacks gather in huge schools numbering up to a thousand individuals. From such a school, pairs separate for mating. During this ritual, one of the fish darkens noticeably. Fertilization is external. Females release up to 1 million eggs. The eggs are 0.7–0.9 mm (0.03–0.04 inches) in diameter and drift freely in the water column, meaning they are pelagic. Sexual maturity is reached at different times, with females maturing later than males. Males typically mature at 4–5 years of age, reaching a length of about 55 cm (22 inches). Females — at 5–6 years, at a length of about 66 cm (26 inches). This species has an interesting pattern: its juveniles, hatched in the subtropics, can be carried far north by currents, as far as New York. In autumn, the juveniles migrate back south to winter in warm waters. After the eggs are laid and fertilized, the parents show no care for them. This is the so-called 'open-water egg scatterers.

Interesting facts

In the crevalle jack, as in some other fish (for example, in jacks, mackerels, and eels), the blood contains a high level of biliverdin — a green pigment that is a breakdown product of hemoglobin. In most fish, biliverdin is quickly excreted or transformed, but in jacks, it accumulates in the blood plasma, giving it a greenish tint.

Why does the color change when ascending?

Cousteau described how the color of the blood changed when ascending from depth:

At depth — emerald (green) due to high pressure and low oxygen content.

At 55 feet (16 m) — brown.

At 20 feet (6 m) — pink.

At the surface — scarlet (red).

This is related to changes in pressure and the saturation of the blood with oxygen: upon ascent, biliverdin oxidizes, and the blood takes on its familiar red color.

Thus, in the crevalle jack, the blood can be green at depth, but on the surface, it turns red. This is not a pathology, but a normal physiological feature.