Some of the best offshore fishing happens over structure you cannot see. Ledges, canyons, humps, and seamounts force currents upward, bringing nutrients and bait toward the surface. Gamefish like tuna, wahoo, and billfish know this and hold near these features.
Why structure works
When current hits a steep change in depth, water is pushed up the slope. This upwelling carries plankton and small baitfish, which draws larger predators. Structure also gives fish a reference point to hold on as they hunt.
Ledges and drop-offs
A ledge is where the bottom drops sharply from one depth to another. In places like the Florida Keys and Carolinas, the edge of the continental shelf is a classic spot for wahoo, blackfin tuna, and sailfish. Troll parallel to the ledge, zigzagging across the drop so lures pass over both shallow and deep sides.
Canyons
Submarine canyons cut into the continental shelf, especially along the U.S. Mid-Atlantic and Northeast. Canyon walls and tips concentrate tuna, marlin, and mahi in summer and fall. Troll along the walls, around the tips, and along any temperature break that crosses the canyon.
Seamounts and humps
Isolated underwater mountains and humps rise from deep water and create upwelling all around them. In places like the Florida Keys, humps are known for blackfin tuna and amberjack. Troll around the up-current side where bait is pushed up.
Using current
The up-current side of structure, where water first hits it, is often the most productive. Use your plotter and temperature readings to find where current is pushing against the feature.
Reading the sounder
Watch for bait clouds and marks on the sounder as you cross structure. Mark them on the plotter and troll back through. See using a fish finder offshore.
Lures over structure
- A mixed spread of resin lures and bullets covers multiple species.
- Add a deep line on a planer or downrigger to reach fish holding below. See downrigger vs planer.
- High-speed lures for wahoo along ledges.
Combine structure with SST charts to find the hottest spots before you leave the dock.
