The Humps of the Florida Keys
There are a series of humps located on the edge of the continental shelf off of the Florida Keys. Included are GPS and loran coordinates for navigation to four productive seamounts.
There are a series of three humps located on the edge of the continental shelf off of the Florida Keys. These humps are loosely called seamounts, because they are like mountains rising from the ocean floor. Worldwide, there are thousands of these structures. Some are remnants of underwater volcanoes; others may have once been emergent islands. Wherever you find them, seamounts are unique marine habitats.
The Marathon Hump, originally called the West Hump, is 27 miles South East of Marathon and is one of the favorite fishing spots for charter boats and private boats. This hump or mound rises from 1150 feet on the east side to 480 feet from the surface. The Marathon Hump is located almost exactly in the middle of the Gulf Stream where the current runs the hardest. Large eddy currents form from the constant easterly flow of the Gulf stream, forcing bait to the surface. This bait draws larger fish which draws larger fish and so on. On a good day, hundreds if not thousands of terns will be feeding over schooling Black Fin Tuna and Dolphin crashing bait. The feeding frenzy in turn attracts large numbers of sea birds and is a perfect way to find the fish.
The list of gamefish caught on the Hump includes dolphin, wahoo, blackfin tuna, huge amberjack, blue marlin, sailfish, white marlin and big sharks, chiefly makos and great whites. Fishing deep on the bottom, you might catch snowy grouper, queen snapper and a variety of other bottom dwellers. You just never know what you might hook out there but can always sure that the Tuna and Bonita will always give you plenty of great light tackle action and everything else will just be icing on the cake.
Each populations of different species of fish find its own comfort zone, according to depth and water temperature. In the case of the Hump, bottom dwellers prefer to stay close to rocky structure on the seamount, while tuna and bonito are normally seen on the fishfinder at about 100 to 200 feet down. Billfish and other pelagics, such as dolphin and wahoo can be found anywhere in the water column.
The time-proven method for catching blackfin tuna on the Hump is to troll a combination of small artificials and skirted ballyhoo 150 yards behind the boat, at 7 to 8 knots. The captain locates the crown of the Hump and then trolls into the current, oftentimes chasing diving birds, and bait sprays, caused by blackfins chasing schools of flying fish or other baits. Modern techniques for catching blackfin tuna include anything from trolling large deep-diving artificals, run straight from the rod, or on downriggers, to chumming with live bait.
To effectively chum with live bait, the captain runs upcurrent of the crown of the Hump, and then as the bottom begins to rise, dumps several hundred live baits overboard. The schools of bait will dash beneath the boat, in an attempt to hide, but can be easily washed out by kicking an engine in gear. The tuna rise to the bait, and can be caught by sight-casting live bait on spinning tackle, or even using a fly. Many world-record blackfin have been caught while anglers used live chum.
Pulling a big lure on the shot gun line is a good idea. Marlin, makos, wahoo and bigger yellowfin tuna, like eating blackfins. They don't always want to play, but the hump is a great place to hook a fish of a life time. A few miles south of the hump is the wall. Here the water drops to over 1000 feet. A great place to dust off those big marlin lures and see how they work. If you find birds working, get ready for just about any pelagic you can imagine.
How to Get There
Here are the GPS and loran coordinates for navigation to four productive seamounts off the Florida Keys. Latitude and longitude are in degrees, minutes and tenths, so set your GPS unit accordingly. The humps are fairly substantial bottom features, and slight aberrations in GPS or loran accuracy are easily remedied by keeping an eye peeled for rips formed by current changes, birds feeding overhead and other boats working the area. A depthfinder will also prove useful. Coordinates given for the Key Largo Hump, listed below, are based on a rough midpoint; it's actually less of a hump and more of an "S" curve between 280 and 330 feet off French Reef.
- Key Largo Hump GPS: 25-00.661' N; 80-16.8'W -- Loran: 14133.7; 43217.8 Depth: 280-330 ft.
- Islamorada Hump GPS: 24-48.175' N; 80-26.674' W -- Loran: 14098.3; 43266.4 Depth: 294 ft.
- 409 Hump GPS: 24-35.5' N; 80-35.5' W -- Loran: 14064.6; 43311.8 Depth: 409 ft.
- Marathon Hump (West Hump) GPS: 24-25.528' N; 80-45.328' W -- Loran: 14032.3; 43358.5 Depth: 516 ft.