Blackfin Tuna Charter Fishing at the Marathon Hump
In this shaded relief image of the Marathon Hump, courtesy of CMOR Mapping, the seamount is clearly visible. The depths shown are in fathoms (1 fathom = 6 feet).
The Marathon Hump is a prominent seamount approximately 25 miles south of Marathon with a justifiably famous year-round fishery for blackfin tuna. It’s also one of our favorite destinations on charter trips. In addition to blackfin tuna, the Marathon Hump regularly produces big mahi (dolphin), sailfish, sharks (which can be a problem) and occasionally wahoo and marlin. Nearby deep-dropping spots allow us to cap off our day of offshore fishing with great eating species like queen and yelloweye snapper, snowy and yellowedge grouper, rosefish and golden tilefish.
The Marathon Hump is situated squarely in the path of the powerful Gulf Stream and rises from a depth of around 850 feet on its west (upcurrent) side to around 500 feet at its peak. Like a huge boulder on the bottom of a river, it accelerates the Gulfstream water and deflects it upward, creating a strong upwelling of cooler water loaded with bait and gamefish. On the east, (downcurrent) side of the seamount, the bottom drops to more than 1,100 feet.
Blackfin tuna closely resemble yellowfin and bluefin tuna in appearance but grow to only about 50 lbs.
Blackfin tuna, our primary target species on Marathon Hump trips, closely resemble bluefin and yellowfin tuna in both appearance and food quality. They don’t grow nearly as large as those species, though. We catch them most commonly in the 12- to 25-lb. range. A 30-pounder is a notable fish, and the all-tackle world record is a little over 45 lbs. Smaller fish in the 4- to 10-lb. range are commonly caught while trolling.
Even an average size blackfin puts on a spectacular fight on appropriate tackle, with sizzling runs followed by a stubborn, deep battle. These fish yield beautiful, thick, sashimi-grade fillets that are delicious raw or seared.
Live Baiting, Jigging and Trolling for Blackfin Tuna
There are a lot of different ways to catch blackfin tuna at the Marathon Hump; the most common are trolling, vertical jigging, and live baiting.
Trolling can put a lot of fish in the boat, but it isn’t our preferred method for a couple of reasons. First, trolling isn’t as exciting for our anglers as other methods. For anglers, trolling mainly consists of sitting and waiting while the captain trolls in circles and then, when a fish is hooked, pulling the rod out of the rod holder and reeling it in. The angler doesn’t have a very active role. Second, trolling tends to produce smaller fish than other tactics.
Live bait fishing for blackfin tuna at the Marathon Hump is more fun for anglers and produces significantly larger fish on average than trolling.
Vertical jigging usually produces larger fish, which tend to stay fairly deep, below the small fish, and it also gives anglers a more active role. The problem is that sometimes that role is too active. Vertical jigging, simply put, is a lot of work, and it can get tiring fast — especially on hot days. For anglers who are physically prepared, jigging is productive and a ton of fun.
Our preferred method at Superfish Charters is live bait fishing for blackfin tuna. We load our wells to the brim with bait and then drift the upcurrent slope of the Marathon Hump. While drifting, we freeline live baits and chum heavily with live baitfish to bring the larger tuna up from deeper water. Often, this triggers a frenzy of jumping fish around the boat and multiple hookups. Everybody aboard is involved, and the action is fast and exciting. For live baiting, we use 25-lb. spinning gear, which is easy to handle for anglers of all sizes and makes for great fights.
Live baiting is exciting and productive, but it requires a lot of bait — and a lot of work. We normally leave the dock at 4 a.m. before a Marathon Hump trip to make sure we stuff all of our wells full of fresh bait.
So what are the downsides to live baiting? First, with all the chum in the water and relatively light gear, sharks can be a problem. The Marathon Hump is home to large numbers of big sharks that will eat hooked fish. Losing a few fish to sharks is par for the course, but sometimes they get so bad that we’re just feeding sharks and have to try a different approach.
Second, obtaining enough bait day after day to effectively live bait the Marathon Hump requires a considerable investment of time and/or money. At Superfish Charters, we operate our own bait skiff and either catch bait in the evenings after the day’s charter or leave the dock at 4 a.m. to fill the wells before the trip. It makes for long days, but, in our opinion, it’s worth it, since live baiting is both more fun and produces bigger tuna.
Keep in mind that not all Marathon Hump charter fishing trips use live bait. Trolling in circles is a lot easier and still puts fish in the boat. If you want to fish live bait, be sure to ask any charter operator you talk to about whether they typically troll or fish live bait, and about the current availability of bait.
Any Season, Any Weather
Rough weather at the Marathon Hump reduces the number of boats in the area, making it easier to chum fish up and keep them feeding around the boat.
There’s no sugar-coating this. At 25 miles offshore with strong currents, seas at the Marathon Hump are rarely calm, and fishing there makes for a long day. Within reason, we will make the trip in any weather our guests are comfortable with. Our fast, capable SeaVee and Whitewater boats get us there and back comfortably and safely.
In fact, rougher conditions actually make the fishing better. The blackfin tuna at the Marathon Hump are notoriously boat-shy; feeding schools will disappear when a boat trolls close to or through them — which happens all too frequently. Rougher conditions cut down dramatically on the number of boats fishing the area, which makes it easier to attract tuna with chum and keep them feeding around the boat.
Blackfin tuna can be caught at the Marathon Hump year-round. Conditions are typically calmer from late spring through early fall, but for larger fish late fall and winter are best.