The Hills are Alive

Amid Barren Seafloor, Isolated Seamounts Provide Epic Encounters

Matt Arnholt October 17, 2018

From backcountry to blue water, the islands that make up the Florida Keys yield access to some of the most productive fisheries in world. Among the most popularized venues near this historic island chain are the numerous offshore seamounts, locally known as the humps. In contrast to the sloping continental shelf that’s largely devoid of life, these deep water structures formed by ancient volcanic activity are densely inhabited and the home to remarkable biological communities providing unparalleled biodiversity.

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Photography: Doughertyphotos.com

As seasons change, varying conditions influence game fish migrations and the prevalence of certain species within the many inshore and offshore venues surrounding the Florida Keys. As a result, anglers are constantly assessing different factors and environmental conditions to determine the most effective and efficient ways of getting connected. However, there are times when local fisheries are unpredictable and certain pursuits are simply hopeless. Fortunately for Keys anglers, the humps provide a level of dependability where a variety of game fish species congregate and feed. No matter the season, something is always biting at the humps.

Offshore of the Middle Keys, the seafloor takes on a unique attribute with powerful Gulf Stream currents slamming into submerged seamounts. Capable of blocking as much as half the water column, but never reaching the surface, seamounts produce cold upwellings of oxygen-rich water that’s forced to increase speed and rise through the water column as it’s deflected from the deep. Nutrients like nitrates and phosphates, which promote the growth of phytoplankton, are also shuffled to the surface in the photic zone where productivity in plankton production cascades up the food chain attracting a host of inhabitants within a complex web of life.

The productivity of these areas is no secret among the Florida Keys fishing community and anglers rarely, if ever, have any of the spots to themselves. On any fishable day of the year, it’s generally a safe bet that there will be boats plying the fertile waters around the most popular humps, which include the Islamorada Hump, 409 Hump and Marathon Hump. However, amid this pressure, the game fish that call these areas home are abundant. While some avoid the humps because of the inherent crowds, the most successful anglers study the bathymetry and associated dynamics of current deflection to determine the manner in which nearby game fish feed, ultimately learning how to adjust their strategies accordingly.

Before any baits or lures hit the water, anglers should take some time to assess the situation at hand and position themselves properly according to the layout of the seafloor below. If you’re planning on fishing in the Keys, we highly recommend purchasing the CMOR Mapping (cmormapping.com) Florida Keys chart card.

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The Marathon Hump rests about 25 miles southeast of Marathon and rises from over 1,000 feet to roughly 480 feet below the surface, right in the path of the Gulf Stream. Unlike other humps in the region, this deep structure is actually two humps about 200 yards long each. While every day is different, in general the largest fish will be found here, compared to the Islamorada Hump, which is only the size of a football field. Only about 12 miles from Snake Creek Channel, the Islamorada Hump rests in about 600 feet of water and rises to within 300 feet of the surface.

While wind, current and bathymetry heavily influence the way these areas are fished, the presence of other boats is also one of the most important factors in getting positioned accordingly. For those fishing the humps for the first time, the scene may seem a bit overwhelming with two-dozen boats jockeying for the best position on the relatively small pieces of real estate. However, anglers can certainly coexist here by exercising common courtesy and understanding the basic etiquette associated with fishing these venues. With that being said, different fisheries around the state have various localized guidelines of what’s deemed too close. Truth is, boats here often fish very close to one another, but remember that what’s acceptable here would be obscene if you were trolling a weedline in the open ocean.

For many anglers visiting the humps, blackfin tuna are top targets thanks to their year-round presence in the region. The major drawback to the constant boat traffic is that it drives larger tuna—fish weighing in the mid to high teens—to sound deeper in the water column. Though juvenile blackfin only a few pounds in weight are numerous, aggressive and can be trolled from dawn to dusk on a variety of artificial lures any day of the year, the larger fish aren’t fooled as easy. This is where and when blacked out baitwells are highly desirable.

By tossing a few frisky live baits overboard, anglers can quickly ignite the bite. Blackfin tuna are equipped with relatively large eyes and rely on excellent eyesight to feed throughout the water column. By strategically tossing a few baits at a time while drifting, anglers capture the attention of tuna cruising below the surface.

Interestingly, one would think the happily freed pilchard would scatter in every direction, but that would spell instant death, an inevitable fate every single baitfish will ultimately meet nonetheless. Instead, the fearful sardines seek safety in numbers and swarm close to the boat, searching for any sort of cover from the menacing pack of feeding tuna below. And while common knowledge claims low light conditions are when tuna bites erupt, at the humps it’s the clear, sunny days that are the most productive. The larger blackfin, pushed deep from boat traffic, can zero in on the shimmering baitfish from a much greater distance in the bright conditions.

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Photography: Doughertyphotos.com

Once these prolific predators key in on the forage above, they aggressively attack the surface and the feeding frenzy begins until no bait remains. As soon as the surface blitz commences, it’s time to pin a bait to a 3/0 circle-hook connected to 20 lb. fluorocarbon leader and send it into the melee. Here, pilchard are the most effective enticements, as these small baits are available in abundance in the Florida Keys and are preyed upon by nearly every offshore predator. When the bite is on, it is common to land dozens of fish before heading back to port with enough sashimi to feed the entire island chain!

While having plenty of live bait on hand is always a good choice at the humps, there are several alternative methods that yield excellent results when executed correctly. Deploying an effective trolling spread at the humps is relatively uncomplicated, but there are a few important details anglers must keep in mind and it’s not as simple as set it and forget it. Since tuna have incredible eyesight, it’s essential that baits and lures are set a long way from the boat, even up to 150 yards to ensure they run in clean channels of water. Several options are effective in this scenario, but small feathers and daisy chains prove irresistible for tuna and other nearby predators. Additionally, a spread of two or three lines is all that’s needed at these venues. This will be enough to handle amid the boat traffic.

Fishing the humps is generally associated with tuna fishing, but there are several other game fish inhabiting these areas that should not be overlooked. Though they don’t provide the same outstanding table fare as blackfin, massive amberjack roam the humps as well. Typically caught at or near the bottom on the up-current side of a hump, these fish will test tackle and skill. With average reef donkeys at the humps weighing around 50 pounds, it’s not uncommon to hook up to a monster weighing upwards of 100 pounds. These fish aren’t picky eaters, devouring live pinfish, grunts, juvenile snapper and much more. Artificial enthusiasts up for a challenge can also entice these beasts with a variety of streamlined jigs. In either scenario, it’s important that enough weight is used to reach bottom in the heavy currents common to these venues. While you stand a great chance of encountering AJ any day at the humps, February through April represents the peak season.

Depending on the time of year, additional pelagic predators like dolphin, wahoo and occasional marlin can be found around the humps. Because there are so many species available, anglers fishing these diverse habitats should be prepared for a wide range of scenarios. Furthermore, sharks at these venues can be menacing and it’s important that anglers use tackle heavy enough to keep hooked fish from getting taxed.

Providing exciting opportunities to get connected, the seamounts of the Florida Keys are certainly unique. Amid the chaos and crowds of fellow boaters, safe boating is essential. And, as local and visiting anglers alike continue to enjoy the fisheries that the humps have to offer, it’s important that we collectively keep conservation a priority and remain sensible when harvesting the game fish that we treasure so much.

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