Caño Negro and the Río Frío

Part of our complete guide: Freshwater fishing in Costa Rica: the complete guide

Caño Negro is the place to hook a tarpon in fresh water, more than 200 kilometres from the sea. The fish swim in from the Caribbean up the San Juan River system and into the Río Frío and the lagoons of the Caño Negro Wildlife Refuge, on the Nicaraguan border, where they share the brown water with snook, guapote and the prehistoric-looking tropical gar. Plan on a lodge-based trip with a guide and a panga, ideally in the high-water months from about August to December, and expect to jump more tarpon than you land.

This guide builds on the Caño Negro section of our complete guide to freshwater fishing in Costa Rica, with more on how the water rises and falls, what a 2026 study found about the tarpon, how the fishing works and the permit you'll need. If you're coming from La Fortuna, our guide to guapote on Lake Arenal covers the other big freshwater trip of the north.

How the refuge and the river fit together

The Caño Negro National Wildlife Refuge covers 9,969 hectares of wetland, forest and pasture in the lower basin of the Río Frío, mostly in the canton of Los Chiles and partly in Guatuso, at just 30 to 44 metres above sea level. It's been a Ramsar wetland of international importance since December 1991, and SINAC, the national conservation agency, runs it through its Arenal Huetar Norte office.

The Río Frío is the backbone. It runs north through the refuge toward Los Chiles and the border, and on into the San Juan, the river that divides Costa Rica from Nicaragua and drains to the Caribbean. That connection is why sea fish turn up here: the tarpon and snook travel inland through the San Juan system, and the 2026 study below describes tarpon migrating about 240 kilometres to reach the fishing grounds.

The water level changes everything:

The fish

When to go

Sources don't line up neatly here, so this is what each one says, and how to read them.

Hotel de Campo says its tarpon are resident and can be fished all year, with no migratory season. The researchers, whose team guides the fly-only programme, describe tarpon arriving with the rains. The practical answer: the high-water months from August to about mid-December are the safest bet for tarpon, the dry months suit gar and fishing tight channels, and you should always check the refuge's open season before you book anything between late March and July.

What the tarpon numbers say

The best data on this fishery comes from a study published in 2026 in the Revista de Biología Tropical by Thomas Enderlin, Maripaz Roldán-Morales and two FECOP scientists, Johel Chaves-Campos and Damián Martínez-Fernández. They counted tarpon bites per day on a fly-only, 100% catch-and-release programme on about 30 kilometres of the Río Frío and its lagoons, from Caño Negro village to the Nicaraguan border, every season from 2014 to 2025 except 2022 and 2023. Each season runs about 15 weeks, from 1 August to 15 December, with up to 4 anglers a week in 2 boats.

What they found is worth knowing before you go:

• Before November 2016, anglers averaged 3 to 8 bites a day.
• Hurricane Otto, the first hurricane on record to cross Costa Rica, came through the northern zone in late November 2016. Bites fell to zero and stayed there until partway through the 2017 season.
• Since then the bite has mostly stayed between 0 and 3 a day, and between 1 and 2 since 2021.

The authors link the drop to the hurricane on top of decades of pressure on the Río Frío basin: wetlands drained for farming, pineapple expansion since the 2000s, farm runoff and sediment. So set your expectations accordingly. A good day might mean a couple of shots at a big fish, and success is counted in tarpon jumped, not landed, as Hotel de Campo puts it.

How it's fished

Almost all of it is from a small panga with a local guide, casting rather than trolling.

Tarpon on the fly

The study's team fishes 12-weight rods, a heavy line that throws big flies and lets you fight a fish fast so it can be released quickly. Enderlin has described anchoring and re-anchoring to keep hooked fish out of the branches and undercut banks, and fish taking a big orange fly stripped across the surface. Most guests are fly-fishing beginners, the study says, so the guides teach casting and fighting on the boat. Hotel de Campo also calls fly fishing the best way to catch the bigger fish.

Tarpon on conventional tackle

Spinning tackle is popular too. Natural Lodge Caño Negro suggests a 6.5 to 8-foot rod, a levelwind reel with a star drag and 150 to 200 yards of 15 to 20-pound line, or saltwater spinning gear, with surface plugs or deep-running lures (a yellow and silver mirror-sided lure is a local favourite), cast from an anchored or drifting boat, or live bait under a float.

Gar, snook and guapote

Gar take live or artificial bait. Snook and guapote hit plugs and soft baits around fallen trees and the lagoon edges. In the dry season, when the water is low and clear, the fish are easier to find but more nervous.

Handling

Keep tarpon in the water for the release, handle gar gently and be careful with the turtles: a Caño Negro guide told The Tico Times that careless anglers snag turtles and injure them taking the hook out. Never lift a big fish by the jaw or gills.

Who to fish with

We chose these on evidence we could check this month (a working, current website or booking page, years in business, recent dates). Nobody pays to be listed.

Permits and the rules

The national rules, from licences to which fish must be released, are in our Costa Rica fishing rules guide.

Getting there and where to stay

Caño Negro village is about 4 hours by road from San José, by way of Ciudad Quesada or via Upala and Los Chiles, and it's an easy add-on to a stay in La Fortuna. The refuge lies about 30 kilometres southeast of Upala. Boats also run up the Río Frío from Los Chiles. A 4x4 helps on the dirt roads in the rainy season. Stay in the village, at one of the two lodges above, so you can be on the water at first light.

If you want saltwater tarpon on the same trip, the fish that pass through here also run the Caribbean river mouths. Our guide to tarpon season on the Caribbean covers the months, Silver King Lodge fishes the Río Colorado, and the wider coast is in our Caribbean fishing guide. For guapote, trout and everything else in fresh water, head back to our complete freshwater fishing guide.