The first thing you notice is the colour. Even in the water, before the fish clears the surface, mahi-mahi announce themselves with a flash of electric blue and yellow-green that seems almost manufactured — too vivid to be real, too sustained to be a trick of the light. Then the fish leaps, turns sideways in the air, and the full spectrum reveals itself: flanks of burnished gold, a dorsal fin running nearly the full length of the body in deep indigo, a tail forked and fast. It hits the water again and the line goes screaming.
Mahi-mahi (Coryphaena hippurus) — known also as dorado or dolphinfish — are perhaps the most visually arresting fish available to the Andaman angler. They are fast, beautiful, acrobatic, and willing. If you have a full day offshore and conditions favour FAD fishing, it is possible to land a dozen fish between dawn and mid-morning, take a spectacular photograph of each, and release them all. Few species reward the effort as generously.
Identification and Biology
The mahi-mahi's appearance is unmistakable. Males (bulls) develop a pronounced blunt forehead as they mature, giving the head a squared-off profile distinctly different from the rounded head of females (cows). Both sexes carry the long, continuous dorsal fin, the deeply forked tail, and the extraordinary colouration — though the precise hues shift rapidly depending on the fish's mood and state of excitement.
In life, mahi-mahi shimmer and change. A fish charging a surface lure pulses with blue and green. When boated or stressed, those colours fade quickly toward yellow-gold and eventually dull grey — which is why photographs taken immediately at the moment of landing, then after a rest in the water, differ so dramatically.
The species is extraordinary in its growth rate, which is among the fastest of any large marine fish. Larvae reach 1 kg within three months. A one-year-old fish may weigh 7–9 kg. Most of the mahi-mahi encountered on Andaman trips are between six months and two years old. This rapid growth, combined with high reproductive output, makes the species naturally resilient — though not immune — to commercial fishing pressure.
Mahi-mahi are typically fish of the open ocean, found in surface waters above the thermocline. They aggregate wherever they find cover: floating debris, weed lines, FADs, and even the shade of a slow-moving vessel. This habitat preference makes them both predictable and vulnerable.
Where to Find Mahi-Mahi in Thailand
The Andaman Sea is the primary fishery. Mahi-mahi concentrate around fish aggregating devices — anchored floating structures designed precisely to attract pelagic baitfish and the predators that follow them — and around natural floating debris such as palm trunks, fishing nets, and weed lines that accumulate during the northeast monsoon.
FADs positioned offshore of Phuket, Phang Nga, and Khao Lak produce consistent mahi-mahi action, and the fish encountered here tend to run in schools of similar-sized individuals rather than the mixed assemblies seen in some other fisheries. The outer Similan Islands and the area extending northwest toward the Burma Banks also hold fish when conditions bring baitfish to the surface.
The Gulf of Thailand produces mahi-mahi far less reliably, though they appear around offshore buoys and structure, particularly in the months following the southwest monsoon. Anglers specifically targeting mahi-mahi should focus their efforts on the Andaman.
Mahi-mahi around a FAD will often hold for surprisingly long periods once a school is established. Local captains who maintain FADs or know their positions keep this information close — a productive FAD is a valuable asset. When asking charter operators about FAD fishing, understand that specific locations may not be shared until you are aboard.
Season and Conditions
The window that suits Andaman offshore fishing broadly — November through April — aligns well with mahi-mahi concentrations. During the northeast monsoon, FADs and natural floating debris accumulate baitfish, and mahi-mahi follow. The clearer, calmer seas of this season also make spotting floating debris easier, which directly translates to more fish found.
The peak months for large fish (over 10 kg) in Thai waters tend to be February through April, when fish that have been feeding through the high season have had time to put on weight. Early season fish (November–December) tend to run smaller but are often more numerous around FADs.
The southwest monsoon (May–October) closes most Andaman offshore fishing, though mahi-mahi do appear occasionally in protected areas during calmer windows in the monsoon.
Techniques
Trolling. The approach that covers ground and locates fish. Running small to medium skirted lures or bibbed minnows at 6–9 knots over likely FAD grounds or along weed lines will draw mahi-mahi readily. Strike one on a trolling rod, slow the boat, and switch to lighter spinning gear — the school will frequently remain in the area.
Spinning and casting. Once a school is located, spinning tackle offers the most entertaining engagement. Small surface poppers (40–80 g), stickbaits, and fast-retrieved metal slices all work well. The key technique for holding a school: leave a hooked fish in the water on a long leader rather than boating it immediately. The distress signals from this fish will keep companions close. When you are ready to release that fish, boat it cleanly and quickly.
Fly fishing. Mahi-mahi are one of the most achievable offshore fly fishing targets available to Thai anglers. They respond readily to large deceiver-style flies in white, yellow, or chartreuse, particularly when the boat is drifting close to a school. A teaser rigged on a conventional outfit to bring fish close, with a fly angler positioned to cast, is the standard method.
Live bait. Small live mackerel or squid drifted near a FAD on a light circle hook will take mahi-mahi when they are not responding aggressively to artificials. This approach suits days when fish are present but not active.
Mahi-mahi do not simply jump — they negotiate with the sky. A hooked fish may leap four or five times in quick succession, each clear of the water by a body length, before deciding to run. The fight is quick, bright, and over before it seems it should be.
Tackle
Light: 20–30 lb spinning setups are the most enjoyable way to fish mahi-mahi. A 3000–5000 size reel loaded with 20 lb PE braid and a 30–40 lb fluorocarbon leader of two metres suits most school fish encountered in Thai waters. Light wire is unnecessary — mahi-mahi have no cutting dentition.
Medium: Where larger fish are expected or trolling is the primary technique, 40–50 lb braid on a 5000–8000 size reel provides reserve. Rod lengths of 2.1–2.4 m give good lure action and casting distance.
Trolling: A 20–30 lb class conventional outfit with a 4/0–6/0 reel running 40 lb monofilament or 50 lb braid handles the trolling approach comfortably. Short, stiff trolling rods of 1.5–1.8 m with roller guides are standard on Andaman charter boats.
Records and Sizes
The IGFA all-tackle record stands at 39.46 kg (87 lb), set in Costa Rica in 1976 — a benchmark that reflects the maximum of what the species achieves. In Thai waters, fish above 15 kg are noteworthy, and anything over 20 kg is exceptional. Most FAD fishing in the Andaman produces fish between 3 and 12 kg.
A school of fish in the 8–12 kg range, encountered on light tackle — which is entirely achievable in season — represents some of the most purely enjoyable offshore fishing Thailand offers.
Conservation
Mahi-mahi's rapid growth and high reproductive rate make it one of the more resilient pelagic species. However, because they aggregate so predictably around FADs, concentrated commercial fishing can deplete local populations quickly. Sport fishing pressure in the Andaman remains light relative to other mahi-mahi fisheries globally, but the trend toward more organised offshore sport fishing warrants responsible habits.
Catch-and-release is strongly encouraged, with one fish for the table being the reasonable limit per vessel. The fish suffer surprisingly little from a well-managed fight and quick release — their vitality when returned is almost immediate if the fight has not been prolonged.
What Hooking One Feels Like
Mahi-mahi strikes are theatrical events. The fish does not simply take — it runs at a surface lure with intent, bursts on it in a spray of white water, and the rod loads hard before you have fully processed what happened. The first run is fast and shallow, often immediately followed by a leap that covers two metres of air. The jumps continue, interspersed with runs that, while not as long or powerful as those of a tuna or wahoo, carry real urgency.
The fight of a 10 kg mahi-mahi on 20 lb gear lasts between five and fifteen minutes of genuine engagement. At no point during that time does the fish stop trying, which distinguishes it from many species that relent once the initial run is over. When you bring it alongside, the colour is extraordinary — and then you watch it fade as the fish rests in your hands. Return it quickly and watch the colours come back, and you will understand why catch-and-release of mahi-mahi feels not like abstinence but like the right ending.
Explore more Andaman pelagic fishing in our guides to sailfish season in Thailand, wahoo, yellowfin tuna, liveaboard fishing, and the comprehensive Andaman Sea fishing guide.
