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How to Tell Yellowtail, Almaco Jack & Cabo’s Jacks Apart

Five jacks and the roosterfish turn up off Cabo San Lucas, and several of them share silver flanks, forked tails and a yellow stripe. Color is the weakest clue. The checks that hold up are structural: bony scutes on the lateral line, detached finlets, where the upper jaw ends and the shape of the fins, as described by the Smithsonian’s Shorefishes of the Tropical Eastern Pacific, FishBase and IGFA.

California yellowtailCalifornia yellowtailAlmaco jackAlmaco jackRainbow runnerRainbow runnerPacific crevalle jackPacific crevalle jackBigeye trevallyBigeye trevallyRoosterfishRoosterfish

Quick key: check in this order

  1. Long, comb-like spines on the back, or two curved black bands running down the flanks to the tail base?Roosterfish. The comb folds into a groove along the back, so on a calm fish look for the two bands and the black lower base of the pectoral fin.
  2. Run a finger along the rear half of the lateral line toward the tail: is there a row of hard, bony scutes?It’s a Caranx: toro or bigeye trevally (go to the last step). No scutes means yellowtail, almaco jack or rainbow runner.
  3. No scutes, and a tiny detached finlet of two rays behind both the second dorsal and the anal fin?Rainbow runner. It also wears a yellow stripe between narrow blue stripes on a slim, torpedo-shaped body.
  4. No scutes, no finlets, and the back clearly more arched than the belly, with long curved lobes on the second dorsal and anal fins?Almaco jack (pez fuerte). Its upper jaw ends below the middle of the pupil, and a dark band often runs from the nape through the eye.
  5. No scutes, no finlets, back and belly curving about equally, and the upper jaw ending below the front edge of the pupil?Yellowtail. Expect a bronze stripe that turns yellow toward the tail and yellowish fins, but confirm with the shape and the jaw.
  6. Scutes present: is there a black blotch at the lower base of the pectoral fin?Toro (Pacific crevalle jack). No pectoral spot, a white tip on a dark dorsal lobe and a fully scaled breast mean bigeye trevally.

Side by side

YellowtailAlmaco jackRainbow runnerPacific crevalle jackBigeye trevallyRoosterfish
FamilyCarangidae (jacks)Carangidae (jacks)Carangidae (jacks)Carangidae (jacks)Carangidae (jacks)Nematistiidae, its own family
Scutes on lateral lineNoneNoneNone35–42 strong scutes27–36 strong, usually dark scutesNone
Detached finletsNoneNoneTwo-ray finlet behind dorsal and analNoneNoneNone described
Body shapeSlim; back and belly curve alikeDeeper; back more arched than bellyLong, slender torpedoModerately deep, oblongFairly elongate; relatively large eyeElongate, compressed; pointed head
Strongest color markBronze midline stripe turning yellow; yellowish tailDark band from nape through eyeYellow stripe between narrow blue stripesBlack spot on gill coverSmall black spot atop gill coverTwo curved black bands on flanks
Pectoral finShorter than headShorter than headShorter than headLonger than head; black blotch lowLonger than head; no spotVery long, curved; black lower base
Where you meet itPelagic schools; rocky shores, reefs, islandsOuter reef slopes, offshore banksOpen sea; around floating debrisNearshore; common in estuariesRocky shores, reef drop-offsSurf and sandy bottoms
Spanish namesJurel, jurel de CastillaPez fuerte, medregal limónMacarela salmónToro, jurel toroJurel ojón, ojónPapagallo, pez gallo
IGFA all-tackle record109 lb 2 oz (49.5 kg), Japan132 lb (59.87 kg), La Paz37 lb 9 oz (17.05 kg)39 lb (17.69 kg)31 lb 8 oz (14.3 kg)114 lb (51.71 kg), La Paz

Swipe sideways on a phone to see all six.

Species by species

California yellowtail

California yellowtail

Seriola dorsalis
  • Elongate body with the upper and lower profiles curving about equally, and a long, pointed snout
  • Upper jaw ends below the front edge of the pupil, and the bone above the rear of the jaw is narrow
  • No scutes and no finlets, but a slight fleshy keel on each side of the tail base
  • Blue back, silvery to white sides, a narrow bronze stripe along the middle that turns yellow toward the tail, and yellowish fins including the tail

Common mistake: A yellow stripe doesn’t make it a yellowtail: the almaco jack usually has one too. Check the profile and the jaw. And in Mexico “jurel” is also part of the names of jacks like the jurel toro and jurel ojón, so ask which jurel.

Almaco jack

Almaco jack

Seriola rivoliana
  • Relatively deep body, with the head and back distinctly more arched than the belly
  • Long, curved front lobes on the second dorsal and anal fins; the dorsal lobe is 16–25% of fork length
  • Upper jaw ends below the middle of the pupil, and the bone above its rear is very wide
  • An oblique dark band from the nape through the eye, often kept by adults, plus a yellow midlateral stripe that is usually present

Common mistake: Its stripe can look just like a yellowtail’s, and the nuchal band can be missing, so neither proves anything alone. Judge by the arched back, the tall sickle lobes and where the jaw ends.

Rainbow runner

Rainbow runner

Elagatis bipinnulata
  • A single detached finlet of two rays behind the second dorsal fin and another behind the anal fin
  • Long, slender, torpedo-shaped body with a pointed snout and a small mouth that ends well before the eye
  • Dark olive-green to blue above, white below, two narrow light blue stripes with a broader olive or yellow stripe between them
  • No scutes on the lateral line; the tail base is slender and notched above and below

Common mistake: IGFA lists “rainbow yellowtail” among its names, and the yellow stripe adds to the mix-up. The two-ray finlets and the blue stripes settle it: neither yellowtail nor almaco has them.

Pacific crevalle jack

Pacific crevalle jack

Caranx caninus
  • A straight rear section of the lateral line with 35 to 42 strong scutes
  • A black spot on the gill cover and a black blotch at the lower base of the pectoral fin
  • Breast scaleless except for a small patch in front of the pelvic fins
  • Moderately deep, oblong body; the mouth reaches back past the eye

Common mistake: The bigeye trevally also has a dark spot on the gill cover, so that spot alone doesn’t decide it. The pectoral blotch and the bare breast do.

Bigeye trevally

Bigeye trevally

Caranx sexfasciatus
  • A dark lobe on the second dorsal fin with a white tip, which grows more obvious with size
  • A small blackish spot at the upper corner of the gill cover, much smaller than the pupil, and no spot on the pectoral fins
  • Breast completely scaled; 27 to 36 strong, usually dark scutes on the straight part of the lateral line
  • Fairly elongate body with relatively large eyes

Common mistake: Juveniles look nothing like the adults: they are golden yellow with 4 to 7 broad dark bars. Count on the scutes and the white-tipped dorsal, not the color.

Roosterfish

Roosterfish

Nematistius pectoralis
  • A first dorsal fin of very long, filament-like spines, banded dark and light, that folds into a deep groove along the back
  • Two dark blue or black curved bands on each flank, running down toward the front of the anal fin and then back along the side to the tail base
  • Very long, curved pectoral fins with a black patch on the lower base
  • Small, smooth scales with no scutes on the lateral line

Common mistake: It isn’t in the jack family. It sits in the same order as the jacks, Carangiformes, but in its own family, Nematistiidae. Its black pectoral base can recall a toro’s blotch, but a roosterfish has no scutes.

Tips for identifying them

Feel before you look. A row of hard scutes along the rear lateral line is the quickest way to split Cabo’s jacks in two: the toro and the bigeye trevally have them, while yellowtail, almaco jack, rainbow runner and roosterfish don’t. FishBase’s yellowtail page (filed under Seriola lalandi) calls it “the only jack without scutella on the caudal peduncle,” but the Smithsonian’s Tropical Eastern Pacific guide describes the almaco jack and the rainbow runner without lateral-line scutes too, so the scute check tells you the group, not the species.

Don’t trust yellow. The yellowtail, the almaco jack and the rainbow runner can all show a yellow stripe, and the almaco’s dark nape band may be missing on adults. Young fish confuse things further: small yellowtail carry numerous narrow dark bars, young almaco jacks up to about 18 cm show a dark nape bar and six body bars plus a seventh on the tail base, and young bigeye trevally are golden yellow with 4 to 7 dark bars. Young almacos are often found far offshore around floating objects.

On deck, settle a yellowtail-or-almaco call with three looks: the profile from the side (equal curves or a high back), the end of the upper jaw against the pupil, and the second dorsal raised to show whether it rises into a long sickle. For a toro or a bigeye trevally, lift the pectoral fin and check its lower base, then look at the breast. If the fish is for a tournament or a record claim, photograph each of those details before it goes in the box or back in the water.

Questions

Is a yellow stripe proof of a yellowtail?

No. FishBase describes a yellow stripe along the side as usually present on the almaco jack, and IGFA notes an amber stripe from the eye along the body on some fish. The rainbow runner has one too. On a Seriola, separate them by body profile, the end of the upper jaw and the second dorsal lobe.

Is the roosterfish a jack?

Not in the family sense. The jacks are Carangidae, while the roosterfish is the only species in its genus and is placed in its own family, Nematistiidae, within the same order, Carangiformes. It is also an inshore fish of the surf and sandy bottoms, rather than of the offshore banks.

How do I tell a toro from a bigeye trevally quickly?

Lift the pectoral fin. The toro has a black blotch at its lower base and a mostly bare breast. The bigeye trevally has no pectoral spot, a fully scaled breast and a dark second-dorsal lobe with a white tip. Both have a spot on the gill cover, so don’t rely on that.

Where were the IGFA world records for these fish caught?

Two of them came from La Paz: the almaco jack, 132 lb (59.87 kg) in 1964, and the roosterfish, 114 lb (51.71 kg) in 1960. The rainbow runner record, 37 lb 9 oz, is from Isla Clarión in 1991. The California yellowtail record, 109 lb 2 oz, was caught in Japan in 2009.

By Max VargasTop Anglers, Cabo San Lucas · international judge at big game fishing world championships · reviewed October 2026

Sources

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