Food from the deep
Cold, nutrient-rich water rises, setting off plankton blooms that feed sardines, mackerel and squid.
Fish Costa Rica · Offshore science
Seamounts of Costa Rica
Hidden underwater mountains far off the Pacific coast are the engine behind Costa Rica’s marlin fishing. What seamounts are, why they hold so many fish, where the main ones are, and how captains fish them.
~12,000 ftOcean depth at the base
800–1,000 ftBelow the surface at many peaks
Nature’s FADsBait gathers, predators follow
May–OctoberPeak marlin season
What is a seamount?
A mountain
you’ll never see.
A seamount is an underwater mountain, usually an ancient volcano, that rises from the deep ocean floor but doesn’t reach the surface. Off Costa Rica, many rise from around 12,000 ft deep to within 800–1,000 ft of the surface.
When deep ocean currents hit a seamount, they’re forced upward, carrying cold, nutrient-rich water toward the light. That feeds plankton, which feeds bait, which brings in the big predators.
Why they hold fish
Four reasons the fish
stack up.
Eddies & breaks
The mountain creates eddies and temperature breaks in open ocean that trap bait.
Predictable flow
Steady Pacific currents and tides make the feeding zones fairly predictable.
The original FAD
Seamounts gathered fish long before man-made FADs were anchored nearby.
The food chain
From plankton to marlin.
- Plankton & krillThe base
- BaitScad, mackerel, sardines, flying fish, squid
- Mid predatorsDorado, yellowfin tuna
- Apex predatorsBlue & black marlin, sailfish
Also around the seamounts: amberjack, grouper, snapper and sharks, plus spinner dolphins and sea turtles. Species guides: blue marlin · black marlin · yellowfin tuna · dorado
Where they are
Costa Rica’s offshore hotspots.
A corridor of seamounts runs offshore from Herradura Bay and Los Sueños, south past Quepos and the Osa Peninsula, toward Cocos Island.
Furuno Bank
A well-known bank offshore from Quepos. Mixed sailfish and blue marlin action, and a classic overnight target.
Overnight tripsThe FAD zones
Numbered FAD zones near the seamounts, far offshore, where crews run for blue marlin.
2–4 day FAD tripsCocos Ridge
A volcanic ridge running toward Cocos Island, with remote water full of pelagics.
Long-range, 3–5 daysThe Thermal Dome
A seasonal upwelling area far off the Gulf of Papagayo, rich in bait, tuna, dolphins and billfish.
Expedition range
How captains find them
Sonar, satellites
and secret numbers.
- Sonar (Furuno, Simrad) to find bait balls and thermoclines
- Satellite charts showing temperature breaks and chlorophyll lines
- Local knowledge: veteran captains keep decades of their own numbers for ridges and humps that aren’t on public charts
- The moon: many crews like to plan around the new moon and first quarter
What it’s like
Electric-blue water.
After a long run offshore, the water turns a deep electric blue and flying fish scatter ahead of the boat. Teasers and dredges go out, and the action can come fast: marlin up in the spread, tuna schools, and sailfish between bites.
On the best days crews can raise marlin after marlin. Some days are slower. That’s offshore fishing, and it’s why multi-day trips pay off.
When to go
Seamount seasons.
May–October · Peak
Warm currents and abundant surface bait make this the best marlin season over the seamounts.
December–April
Calmer seas, with sailfish runs closer to shore. Most anglers fish day trips this time of year.
Conservation
All billfish are catch-and-release by law in Costa Rica. Crews use circle hooks, keep fish in the water and record releases. Catch and release →
Fish the seamounts
Plan your trip.
The guideFAD fishing in Costa RicaHow multi-day marlin trips to the FADs and seamounts work.Read the FAD guide →
2–4 daysFAD fishing packagesPrivate long-range expeditions with everything aboard.See packages →
1–2 nightsOvernight chartersA first night offshore, with banks like Furuno in range.Overnight charters →
Seamount questions
Quick answers.
Curious about a seamount trip? Ask us.
What is a seamount?
An underwater mountain, usually an ancient volcano, that rises from the deep ocean floor without reaching the surface. Off Costa Rica, many rise from around 12,000 ft deep to within 800–1,000 ft of the surface.
Why do seamounts attract fish?
Currents hitting the seamount push nutrient-rich water upward, which feeds plankton and bait. Eddies and temperature breaks around the mountain trap the bait, and predators like marlin, tuna and dorado follow.
Where are Costa Rica’s main seamounts?
In a corridor offshore from Los Sueños and Quepos south toward the Osa Peninsula and Cocos Island, including Furuno Bank and the Cocos Ridge. The Thermal Dome is a seasonal upwelling area far off the north-west coast.
How long is a seamount fishing trip?
Most seamount trips take 2–4 days, sleeping on the boat. Closer banks like Furuno are within reach on an overnight trip, and the Cocos Ridge needs 3–5 days.
When is the best time to fish the seamounts?
May to October is the peak marlin season over the seamounts.
Plan your expedition
Fish where the
mountains hide.
Tell us your dates, how many days you can spend offshore, and your group size. We’ll match you with the right boat and seamount.
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