Mahi-mahi fishing out of Marathon depends on three things: the months, a 30-45 minute run to Gulf Stream water, and which structure to put on the plotter. This guide covers when the fish are around, how far boats run, the named grounds with depths, how this port trolls, and who fishes for them.
When mahi run off Marathon and how far boats go
Biology, general rigging and spreads are in the mahi-mahi species guide. This page covers Marathon specifically: which months to plan around, and how long the run to Gulf Stream water takes from the Middle Keys.
Season
Local operators put the window in the same place:
- Always Late: "Peak season runs from April through September."
- Memory Maker: mahi "really turn on during the warmer months."
- Infinite Blue: "The peak season runs from late spring through early fall."
For the regional migration picture beyond Marathon, see the Atlantic Southeast mahi guide (see also the wider Atlantic Southeast guide).
The run
Memory Maker and Always Late run 30-45 minutes to grounds in Gulf Stream water. That time is measured to the water the fish are in, not to a fixed waypoint. The Marathon port guide covers the channels out of the harbor, ramps, marinas, and where to read the forecast and buoy numbers.
Grounds and structure off Marathon
Work from the moving features to the fixed ones. Infinite Blue fishes the Marathon Hump along with Gulf Stream debris, weedlines and current edges. Weedlines, debris and edges shift day to day, so treat named structure as a starting point rather than a fixed address.
| Ground | Depth | Structure | Distance |
|---|---|---|---|
| Marathon Hump (Marathon West Hump) | 480 ft at shallowest point | Rise in Gulf Stream water | Not listed |
| 409 Hump (also listed as 408 Hump) | Not listed | Named Middle Keys blackfin spot | Not listed |
| Thunderbolt | 120 ft | Wreck | 4 miles south of Marathon and Key Colony Beach |
| Marathon Reef Site | About 100 ft | Bridge rubble | Not listed |
| Seven Mile Bridge Reef | 90 ft | Bridge spans and concrete | Not listed |
| Long Key Reefs | 24 and 26 ft | Bridge spans and concrete | Not listed |
Chart layers are not for navigation. Cross-check every position against the official chart and the NOAA Coast Pilot chapter for Miami to Key West.
Marathon Hump
The shallowest point on the Marathon Hump, also called the Marathon West Hump, is 480 ft. It is a rise in Gulf Stream water and the named structure Infinite Blue works for mahi.
409 Hump
The spot is listed as both the 409 Hump and the 408 Hump, and it is named as a top Middle Keys blackfin spot. For the other pelagics found here and at the Marathon Hump, see the offshore gamefish guides.
Thunderbolt
Thunderbolt sits in 120 ft of water, 4 miles south of Marathon and Key Colony Beach.
Bridge reefs and rubble
From deep to shallow, the bridge-related structure inside the run is:
- Marathon Reef Site: bridge rubble at about 100 ft.
- Seven Mile Bridge Reef: bridge spans and concrete at 90 ft.
- Long Key Reefs: bridge spans and concrete at 24 and 26 ft.
How Marathon boats fish for mahi
Offshore trolling is the local method, worked along the moving features that hold fish in Gulf Stream water.
Trolling the Stream
Infinite Blue runs an 8-hour trolling trip, and Southern Sons runs a trolling trip. The species guide linked above carries the rigging detail.
Weedlines, debris and edges
Infinite Blue works Gulf Stream debris, weedlines and current edges. Those features drift, so the daily decision is where to look first, since the fish won’t stay in one place.
Who fishes mahi out of Marathon
Charter captains and tournament crews both work these grounds.
Charters
Four Marathon charters list mahi-mahi:
- Always Late Fishing Charters: captain Lucas Ponzoa. Always Late, a 32-ft SeaVee center console, 6 passengers.
- Memory Maker Sportfishing: captain Jon Henry. A 29-ft SeaVee center console, restored 2000 model.
- Infinite Blue Charters: captain Robert Williams. Happy Ours II, a 47-ft Sea Ray, and a Wellcraft 290 Coastal.
- Southern Sons Charters: captain Josh Cox.
Tournaments
Three dolphin tournaments run out of Marathon, in calendar order:
- Tom Thumb Marathon Offshore Bull & Cow Dolphin Tournament (usually April)
- Mother’s Day Dolphin Tournament (usually May)
- Father’s Day Dolphin Derby (usually June)
All three fall inside the April through September peak.
FAQ: mahi-mahi fishing out of Marathon
What are the best months for mahi out of Marathon?
April through September, per Always Late. Infinite Blue says late spring through early fall.
How long is the run to mahi water from Marathon?
30-45 minutes to grounds in Gulf Stream water, per Memory Maker and Always Late.
How deep is the Marathon Hump?
480 ft at its shallowest point. It is also called the Marathon West Hump.
Is it the 409 Hump or the 408 Hump?
Both names refer to the same named spot, a top Middle Keys blackfin spot. No depth is listed for it.
When are the Marathon mahi tournaments?
The Tom Thumb Bull & Cow is usually in April, the Mother’s Day tournament usually in May, and the Father’s Day Derby usually in June.
Where do I find the rules for mahi out of Marathon?
The Florida regulations and federal rules pages. Check which applies before fishing.
