When cobia are around Marathon
Cobia fishing out of Marathon revolves around a spring window and two depth bands. This page covers the timing, how boats work each band, and the named structure with its depths. Biology and general tactics are in our cobia species guide.
Spring migration
Southern Sons Charters puts prime time in the spring migration, March through May. For the wider migration up the coast, see our Atlantic Southeast cobia guide (see also the Atlantic Southeast offshore fishing guide).
How far and where boats run
The two bands meet at about 30 ft. Inshore is 30 ft or less, and offshore runs from 30 to 70 ft.
Inshore: 30 ft or less
Ana Banana Fishing Company works buoys, wrecks and channel markers in 30 ft or less. The marked structure in this shallow band is easy to pick out on the way in and out of the channels.
Offshore: 30 to 70 ft
Southern Sons Charters works wrecks, reefs and structure in 30 to 70 ft. Compare the named grounds below against these two bands before choosing a run.
Named grounds and structure off Marathon
The table lists the named grounds off Marathon with their depths and where each falls relative to the two bands.
| Ground | Depth | Structure | Note |
|---|---|---|---|
| Long Key Reefs | 24 and 26 ft | Bridge spans and concrete | Inside the 30 ft or less inshore band |
| Seven Mile Bridge Reef | 90 ft | Bridge spans and concrete | Deeper than the 30 to 70 ft band |
| Marathon Reef Site | 100 ft | Bridge rubble | Deeper than the 30 to 70 ft band |
| Thunderbolt | 120 ft | Wreck | 4 miles south of Marathon and Key Colony Beach. Deeper than the 30 to 70 ft band |
| Marathon Hump (Marathon West Hump) | 480 ft at shallowest | Hump | Blackfin ground |
| 409 Hump (also listed as 408 Hump) | Not listed | Hump | Named as a top Middle Keys blackfin spot |
Mark these as waypoints and cross-check depths against Chart Contours. Chart layers are not for navigation. For the bridge rubble and reef sites, the FWC Florida Keys artificial reefs list is a good place to verify before you save anything.
Bridge rubble and reef sites
Long Key Reefs sit at 24 and 26 ft on bridge spans and concrete, inside the inshore band. Seven Mile Bridge Reef is at 90 ft on bridge spans and concrete, and the Marathon Reef Site is at 100 ft on bridge rubble. Both of those are below 70 ft.
Thunderbolt
Thunderbolt is a wreck in 120 ft, 4 miles south of Marathon and Key Colony Beach. That is deeper than the published 30 to 70 ft band.
The deep humps
Marathon Hump has a shallowest point of 480 ft. 409 Hump, also listed as 408 Hump, is named as a top Middle Keys blackfin spot. Both are blackfin ground; for that fishing, see our other offshore gamefish guides.
How it is fished and who fishes it
Two charters list cobia out of Marathon, one for each band.
Southern Sons Charters
Capt. Josh Cox runs a 6 to 8 hour offshore trip working wrecks, reefs and structure in 30 to 70 ft. The operation puts prime time at March through May. Details are on the Southern Sons Charters Guidesly listing.
Ana Banana Fishing Company
Capt. Joel Brandenburg runs an inshore cobia and grouper charter in 30 ft or less, aboard a 1975 40-ft Hatteras with twin Detroit Diesel engines. Details are on the Ana Banana inshore charter page and the Ana Banana Guidesly listing.
FAQ about cobia fishing out of Marathon
When is prime time for cobia out of Marathon?
Southern Sons Charters puts prime time in the spring migration, March through May.
How deep do boats fish for cobia?
Cobia fishing out of Marathon splits at about 30 ft. Inshore is 30 ft or less around buoys, wrecks and channel markers (Ana Banana). Offshore is 30 to 70 ft around wrecks, reefs and structure (Southern Sons).
How far is Thunderbolt from Marathon?
Thunderbolt is 4 miles south of Marathon and Key Colony Beach, in 120 ft.
Are Marathon Hump and 409 Hump cobia spots?
Both are blackfin ground. Marathon Hump’s shallowest point is 480 ft. 409 Hump is also listed as 408 Hump.
Which Marathon charters list cobia?
Southern Sons Charters (Capt. Josh Cox, 6 to 8 hour offshore trip) and Ana Banana Fishing Company (Capt. Joel Brandenburg, inshore cobia and grouper charter).
Where are the cobia rules?
FWC sets the state rules, and they are on our Florida saltwater regulations page. Federal rules apply in federal waters. Check both before you fish.
