They are not the fish you are usually aiming at when one slams the lure — but once you understand what happened and why, you start making plans to find them deliberately. The jack family is vast, its members are distributed across every warm-water reef system on earth, and in Thai waters the genus Caranx and its close relative Carangoides together account for some of the most entertaining light-tackle action available within sight of the beach.
A note on naming: the true jack crevalle, Caranx hippos, is an Atlantic species. It does not exist in the Indo-Pacific. The term "jack" in Thai fishing contexts refers loosely to the broader jack family — carangids — particularly the medium-sized schooling species that pepper reef edges and current lines throughout both the Andaman Sea and Gulf of Thailand. The most important of these for the recreational angler are the bigeye trevally (Caranx sexfasciatus) and several species within the Carangoides genus, including sixbanded trevally (Carangoides sexfasciatus) and coromandel trevally (Carangoides coeruleopinnatus).
Taxonomy and the Thai Jack Family
The family Carangidae contains roughly 30 genera and 150 species globally, making it one of the most species-rich families among commercially and recreationally important marine fish. In Thailand, anglers regularly encounter a dozen or more carangid species, though most do not register by name — they are simply "small trevally" or, in the markets, pla hang khaeng (hard-tailed fish), a catch-all that covers everything from finger-length yellowstripe scad to 8-kg bigeye trevally.
Bigeye trevally (Caranx sexfasciatus) is the most relevant species for recreational purposes. It is a deep-bodied jack with distinctly large eyes — a nocturnal and crepuscular adaptation that makes these fish particularly active at dawn, dusk, and under artificial light at night. Adults typically run 30–55 cm and 1–4 kg, with exceptional fish exceeding 8 kg. The body is silver with a faint yellowish tinge on the flank and a small black spot at the rear margin of the gill cover. Unlike the giant trevally, which often hunts alone, bigeye trevally are obligate schooling fish — mid-water aggregations of hundreds of individuals are common, particularly on current-swept offshore structure.
Sixbanded trevally (Carangoides sexfasciatus) — not to be confused with the bigeye's scientific name — is a separate species frequently encountered in the same reef habitats. It shows six faint bands on juveniles that fade to a uniform silver-gold in adults. Slightly deeper-bodied than the bigeye, it often mixes with bigeye schools on reef edges.
Coromandel trevally (Carangoides coeruleopinnatus) and bumpnose trevally (Carangoides hedlandensis) complete the common roster. All are small to medium carangids, all school, and all hit lures with conviction.
The GT Session Bycatch
On any GT popping or light jigging session in Thai reef water, schooling bigeye trevally and sixbanded trevally are the species most likely to appear between GT strikes. They hit the same lures, fight hard relative to their size, and keep a session lively. Many guides consider them nuisances; most visiting anglers, once they experience the aggression of a school of bigeye on PE1 gear, disagree.
Where in Thailand
Andaman Sea
The Andaman's offshore pinnacles and reef channels hold the highest concentrations. The reefs around the Similan Islands, Koh Bon, Koh Tachai, and Richelieu Rock are classic bigeye trevally grounds — mid-water schools are visible on depth-sounders stacked in the thermocline, often at 10–25 m depth. Current-swept channels between islands in Phang Nga and Krabi provinces are more accessible inshore options, where schools of sixbanded and bigeye trevally push through on tidal movements.
Phi Phi Island's northeast channel, the rocky points around Koh Lanta, and the current-swept passages near Phuket's Racha islands are all within day-trip range of the main tourist centres and regularly produce mixed-species sessions including schooling jacks.
Gulf of Thailand
In the Gulf, bigeye trevally are abundant around the rocky reefs of Koh Samui, Koh Phangan, and Koh Tao. The deep southern Gulf around Chumphon has excellent current systems that aggregate both pelagics and schooling jacks. The offshore FADs (fish-aggregating devices) maintained by fishing fleets in the Gulf are extraordinary aggregation points — bigeye trevally in the hundreds can surround a FAD, visible from the surface as a dark swirling mass.
The upper Gulf around Pattaya and the eastern seaboard also holds these species, though water clarity and overall fish quality are lower than in the southern Gulf or Andaman.
Night Fishing at Piers and FADs
One of the most productive — and least written-about — tactics for bigeye trevally is fishing under lights at night. Piers and jetties with overhead lighting in Phuket, Krabi, Chumphon, and on the Gulf islands aggregate zooplankton, which draws baitfish, which draws schooling jacks. A small metal jig or soft plastic worked through the illuminated water under a fishing pier at 9 pm can produce non-stop action on bigeye and sixbanded trevally, with the occasional snapper, barracuda, and small GT as bonus.
Technique and Tackle
Light-Tackle Topwater
This is where jack fishing stops being incidental and starts being genuinely addictive. Small surface lures — poppers in the 60–90 mm, 12–20 g range, or slender stickbaits of similar size — fished across current lines and reef edges produce surface strikes from schooling jacks that are disproportionately violent relative to the fish's size. A school of bigeye trevally chasing baitfish to the surface, then detonating on a surface lure in the middle of the boil, is a spectacle that remains satisfying regardless of how many times it happens.
Rod: a 7 ft spinning rod rated PE1–PE2 (approximately 10–20 g lure weight). Reel: 2500–3000 size, high retrieve ratio preferred. Braid: PE1.5 (12 lb) provides good sensitivity and casting distance. Leader: 20 lb fluorocarbon, 1.5–2 m. The fluorocarbon matters — schooling jacks in clear water over reefs are leader-shy, and heavy nylon will reduce strikes noticeably.
The retrieve should be active: short, sharp pops on the surface with brief pauses. Bigeye and sixbanded trevally respond to erratic action and will follow a poorly-worked lure for metres without taking. The answer is always more energy in the presentation, not less.
Light Jigging
When fish are holding in the mid-water column rather than near the surface — common in deeper water and on stronger current — small metal jigs fished on a high-speed retrieve or a flutter-fall technique consistently produce. Jigs in the 20–60 g range in natural silver, sardine, or UV blue-pink patterns are the standard. Work the jig from mid-water down and count it back to the school depth indicated on the sounder.
Matching Bait School Size
When bigeye trevally are feeding on a specific bait school — finger mullet, anchovy, small squid — downsizing the lure to match the prey makes a meaningful difference. Anglers who arrive with only GT-sized poppers and wonder why the visible school isn't responding will usually find that a 60 mm stickbait on a light rod solves the problem immediately.
Fly Fishing
The fly approach works exceptionally well for schooling jacks in two scenarios: working shallow reef flats where fish push baitfish into confined water, and night fishing under pier lights where presentation accuracy matters more than casting distance. A 7–9 weight rod with an intermediate line handles both. Small Clouser Minnows in white-and-chartreuse, small Deceivers, and EP baitfish patterns in 5–7 cm sizes are reliable. The take is usually an aggressive strip-set opportunity; the fish run hard on light fly tackle.
Bait Fishing
Live prawns, small live fish, and strips of fresh squid or sardine on small circle hooks fished near reef structure or under pier lights catch schooling jacks consistently and are the most accessible approach for anglers without specialist lure tackle. This is also the most family-friendly option — keep bait small, use light running rigs, and the activity level can be extraordinary.
Season and Timing
The jack family is largely non-seasonal in Thai waters — fish are present year-round in both the Andaman and Gulf. That said, conditions influence quality:
Andaman Sea: November through April (northeast monsoon / dry season) offers the best water clarity and most accessible offshore reefs. Bigeye trevally schools on the outer Andaman reefs are at their most active and visible in this window.
Gulf of Thailand: October through March is generally the most productive period. Cooler water temperatures (27–28°C) increase fish activity. The southern Gulf around Chumphon peaks October–February.
Tidal movement trumps season in most inshore contexts. The first two hours of the running tide — both flood and ebb — consistently produces more jack activity than slack water. Plan sessions to overlap with active tide wherever possible.
Conservation
Schooling species like bigeye trevally are resilient by nature — their reproductive strategy depends on large aggregations, and the species is not commercially overexploited in Thai waters relative to the size of the population. However, in areas close to population centres with high fishing pressure — the upper Gulf, inshore Phuket — decades of net-fishing pressure have reduced the size structure: the average fish is smaller than older accounts suggest.
Releasing schooling fish is both ethical and logical: a school that remains intact in a location will continue providing sport. Taking ten fish from a school of a hundred rarely improves a day's fishing in any meaningful way, and the fish's value as a baitfish and prey item in the reef ecosystem is real. Take one or two if you want fresh fish for dinner; release the rest.
What to Expect on a Mixed Session
The honest description of jack fishing in Thailand is that the species rarely headlines a trip — but it consistently improves one. A GT popping session that goes quiet between strikes, a deep jigging drift that produces nothing larger, an early-morning session on a Gulf reef waiting for Spanish mackerel to show: in all these situations, the appearance of a school of bigeye trevally transforms the session from patience exercise to genuine engagement.
Once you know what the species are and how to find them deliberately — current-swept channels at dawn, FADs at night, lit piers after dark — they become a planned target rather than a pleasant interruption. On PE1 gear with a surface lure and a school actively hunting around you, they are among the most entertaining fish in Thai waters. The fact that a larger, more famous fish shares the same reef is not an argument for ignoring them.
For the broader trevally picture in Thailand, see our guides to giant trevally, bluefin trevally, and brassy trevally. For the Gulf context, the Chumphon fishing guide covers the offshore FAD grounds where bigeye trevally aggregations are most spectacular.
