Rainbow Trout Fishing in Argentina

The rainbow trout is the fish most anglers meet first in Patagonia — hard-fighting, acrobatic and found in nearly every river and lake from Bariloche to Tierra del Fuego. But Argentina hides a secret that has drawn fly fishers from around the world: on a remote steppe lake in Santa Cruz, rainbows grow to sizes that exist nowhere else on earth. This guide covers the rainbow trout across Argentina — the everyday sport fish, the world-famous trophy fishery, and everything you need to know to catch them.

Rainbow trout in Argentina — the facts

• Species: rainbow trout, Oncorhynchus mykiss.
• Status: introduced from the Northern Hemisphere in the early 1900s; now fully wild and self-sustaining.
• Average size: 1–4 lb across most of Patagonia; 8–12 lb at Jurassic Lake.
• Trophy size: 20 lb+ at Lago Strobel (Jurassic Lake).
• Where: everywhere — most numerous trout in the country; the giants live in Santa Cruz.
• Season: November–April in Patagonia; October–April at Jurassic Lake.
• Top tactics: dry fly, nymphing, streamers; sight-fishing from shore at Jurassic.

The fish and its story

Rainbow trout are native to the Pacific drainages of North America, and were shipped to Argentina in the early 1900s as part of the same great stocking effort that brought brown and brook trout to Patagonia. They took to the cold Andean rivers and lakes immediately, and today reproduce entirely in the wild. Rainbows are the most widespread and most numerous trout in the country — the fish you are most likely to hook on a first cast in Bariloche, on the Limay, or on any of the classic float rivers of the north. They are prized for their speed, their willingness to eat a dry fly, and the wild, cartwheeling jumps that make even a modest fish feel bigger than it is.

How big do rainbow trout get?

Rainbow trout can reach remarkable sizes. The IGFA all-tackle world record is a 48-pound fish caught at Lake Diefenbaker, Canada, in 2009 — although that trout was a farm-escaped triploid, and many anglers look elsewhere for the true measure of a wild rainbow. That is exactly what makes Argentina special: at Jurassic Lake, entirely wild rainbows average 8–12 pounds and regularly top 20, the finest wild-rainbow fishing on earth. Across the rest of Patagonia a good rainbow runs 1–4 pounds, with larger fish holding in the big lakes and tailwaters — plenty of pull on a 5-weight.

Jurassic Lake: the world’s greatest rainbow fishery

No conversation about Argentine rainbows is complete without Jurassic Lake, known locally as Lago Strobel — a closed, wind-scoured lake on the Santa Cruz steppe with no outlet to the sea. Rainbows were introduced to its one tributary, the Barrancoso River, only a couple of decades ago, and with a huge food supply and no competition they exploded in size. Today it is widely regarded as the most prolific trophy rainbow fishery on the planet: the average fish runs 8–12 pounds, and trout over 20 pounds are landed every season, almost all of them caught on foot from the exposed shoreline. It is remote — roughly five hours from El Calafate — but for anglers chasing a rainbow of a lifetime, there is simply nowhere else like it. Its season runs from October to April.

Where to catch rainbow trout in Argentina

Beyond the fame of Jurassic Lake, rainbows are the backbone of trout fishing across the country:

• The Limay River and the rivers around Bariloche — strong, wild rainbows in clear tailwater and mountain streams.
• The northern float rivers — the Collón Curá, Aluminé and Chimehuín all hold excellent rainbow populations.
• The big lakes — Nahuel Huapi, Gutiérrez, Mascardi and many others, best fished at the bocas.
• Lago Strobel (Jurassic Lake) and the Barrancoso River in Santa Cruz — the trophy destination.

Rainbow trout vs brown trout

In Patagonia you will often catch both species side by side, so it helps to tell them apart:

• Rainbow trout (Oncorhynchus mykiss): silvery, olive-backed body with a bright pink-to-red stripe down the flank and heavy black spotting that covers the whole tail. Fast and acrobatic, prone to spectacular jumps.
• Brown trout (Salmo trutta): butter-gold flanks with black and rust-red spots ringed by pale halos, few spots on the tail. Warier, more predatory, and often larger. Read our guide to brown trout in Argentina.

One key difference matters on the water: rainbows spawn in spring, while browns spawn in autumn — which shapes when and how each is best targeted.

Rainbow trout vs steelhead

Another common question: what is the difference between a rainbow trout and a steelhead? They are the same species — Oncorhynchus mykiss — but a steelhead is a rainbow that migrates to the sea and returns to spawn, growing larger and turning bright chrome-silver in the process, while a resident rainbow lives its whole life in fresh water. Argentina’s rainbows are freshwater residents rather than true sea-run steelhead, but the chrome-bright giants of Jurassic Lake, fattened in a vast landlocked lake, echo the look and power of steelhead — one more reason the fishery is so prized.

When to go

The Patagonian season runs roughly November to April, and rainbow fishing shifts through it:

• November–December (spring): rainbows spawn and move, and streamer fishing is highly productive as fish are aggressive and on the feed.
• December–February (summer): peak dry-fly and hatch fishing, plus terrestrials — the classic Patagonian rainbow experience.
• March–April (autumn): excellent fishing continues, with rainbows feeding hard before winter. At Jurassic Lake, the shoulder months are prime for the Barrancoso River run.

For a full breakdown, see the best time to fly fish Argentina.

When do rainbow trout spawn?

Rainbow trout spawn in spring — in Patagonia, roughly from September into early summer — when they move onto gravel to cut their nests, or redds. This spring timing is the mirror image of the brown trout’s autumn spawn, and it shapes the fishing: through the early season rainbows are on the move and feeding hard, which is why streamer fishing is so effective in November and December. Because spawning fish are vulnerable, many waters protect gravel spawning areas and enforce catch-and-release, so handle early-season rainbows with extra care.

How rainbows are fished

Rainbow trout are among the most obliging fly-rod fish, and can be caught on the full range of techniques:

• Dry fly: rainbows look up readily, making them ideal for attractor dries, mayfly and caddis imitations, and summer terrestrials.
• Nymphing: a dry-dropper or indicator rig is deadly in the runs and riffles.
• Streamers: stripping baitfish patterns takes the larger, more predatory fish, especially in spring and at the lake mouths.
• Sight fishing on foot: the signature style at Jurassic Lake, spotting cruising giants and casting from shore.

Flies and gear

A 9-foot 5- or 6-weight is the ideal all-round rainbow rod for Patagonia; step up to a 7- or 8-weight for the big fish and wind of Jurassic Lake. Proven flies include Parachute Adams and mayfly imitations, caddis, hoppers and beetles for the surface; Pheasant Tail and Prince nymphs below; and Woolly Buggers and baitfish streamers for the larger fish. As always in Patagonia, come prepared for wind.

Handling and conservation

Most of Argentina’s best rainbow water is managed for catch-and-release, and the culture is strong. Fish barbless, keep the fish wet, minimise handling and air time, and let each trout recover in the current before it swims off. Careful release is exactly why fisheries like Jurassic Lake continue to produce fish of a size found nowhere else.

Plan your Argentina rainbow trout trip

Whether you want fast dry-fly action around Bariloche or a shot at a 20-pound rainbow at Jurassic Lake, we can match you with the lodges and guides who fish this water best. Tell us your dates, budget and style, and we will do the rest.

Frequently asked questions about Rainbow Trout