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catalog Salmonidae · predator

rainbow trout

Oncorhynchus mykiss

Freshwaternon-native in Brazil

Exotic salmonid of cold highland rivers in the Mantiqueira and the Serra Catarinense. The classic fly fishing fish in Brazil.

Also called: truta, truta-arco-íris, rainbow trout

forecast for rainbow trout where found
Scientific illustration of Rainbow trout
common size
25–45 cm
maximum
120 cm
common weight
0.3–1.5 kg
record/max.
25.0 kg
depth
0.3–3 m
ideal water
10–18 °C
overview

who is the rainbow trout

North American fish introduced in the 20th century to cold highland rivers of the Southeast and South, where the water stays below 20 °C. It is exotic and preys on insects, crustaceans and small fish, and can compete with the native fauna of mountain streams. Many populations depend on hatcheries and stocking, and releasing trout into a river without a license is an offense. It is the symbol fish of Brazilian fly fishing: towns like Campos do Jordão, Bocaina de Minas, Visconde de Mauá and Urubici live off trout tourism. In Brazil, most are 25 to 45 cm.

fun facts

  • In many Brazilian rivers the population is kept up by stocking from trout hatcheries.
  • The pink color of the meat comes from a diet of crustaceans or from feed.
how to recognize it

identification

Torpedo-shaped body, olive-green back with many small black spots that extend onto the dorsal, adipose and tail fins. Pink to reddish lateral band. Silver belly. Has an adipose fin and very small scales. No native fish of the highland rivers has this combination. Color varies with the water and age.

how rainbow trout fishing looks

Loading the next 7 days…

Each card shows the day's index (0 to 100) and, below it, a strip with the index for each hour, from 0h to 23h. from poor to excellent.

distribution

where found

open on the large map

Exotic, native to the Pacific coast of North America. Highland rivers of the Serra da Mantiqueira (SP, MG, RJ), the Serra da Bocaina and the highland plateau of SC (Urubici, Bom Jardim da Serra, São Joaquim); trout hatcheries and pay-to-fish trout ponds.

Habitat: Mountain streams and rivers with cold, clear, oxygen-rich water; rapids, pools and slack water behind rocks.

introduced in

Southeast AtlanticParanáUruguay

states

São Paulo, Minas Gerais, Rio de Janeiro, Santa Catarina

calendar and clock

when to fish

best season

time of yearbest: May–Sep
JanFebSeaAprMayJunJulAugSepOctNovDec

Autumn, winter and early spring, with cold water. In summer the water warms, the fish gets stressed and releasing it is risky.

best time of day

0h6h12h18h sunrise ~6amsunset ~6pm

Daytime, with peaks at dawn and dusk. Active during the day, peaking at dawn and in the late afternoon, when insects hatch.

weather, water and behavior

what affects the rainbow trout
sensitivity The little bars show how much each factor affects this species. Five full: it feels it a lot.

cold and cold fronts

Likes cold water; the problem is heat, not cold.

atmospheric pressure

A sudden change reduces insect hatches and activity.

moon

Little effect.

rain

Muddy runoff clouds the stream and stops fishing.

water level

Low, clear river is better; summer floods hurt.

noise

Very wary: approach from downstream, without casting a shadow over the pool.

wind

Hinders dry fly casting.

depth

Shallow in the rapids and at pool heads; the pool bottom in strong sun.

technique, gear and bait

how to fish

Fly fishingMid-water casting
rod
fly #3 to #5, 7'6" to 9'; or ultralight 5' to 6', 2 to 6 lb
spinning / baitcasting reel
simple fly reel or 1000 spinning reel
line
WF floating fly line; or monofilament 0.16 to 0.20 mm
leader
9' 4X to 5X fly leader; fluorocarbon 4 to 6 lb on spinning
hook
flies #12 to 18, barbless

lures

  • spinner #0 to 2
  • small spoon 2 to 5 g
  • nymphs (pheasant tail, hare's ear)
  • dry flies (elk hair caddis)
  • streamer woolly bugger

natural baits

  • earthworm (where permitted)

accessories

  • rubber passaguá
  • wader
  • polarized glasses
  • water thermometer

tip from an angler

Cast above the pool and let the fly drift naturally. With water above 20 °C, don't fish: the trout suffers and dies after release.

guide

fly fishing in brazil: first steps

How to choose gear by its number, rig the backing, line, leader and tippet, make a basic cast, and which flies to use for peacock bass, golden dorado and snook.
what the law says

rules for the rainbow trout

Summary of the regulations we found, with the source for each. Rules change; before keeping or transporting fish, check with the state environmental agency.
Conservation: Potential impact on the native fauna of highland streams.

Releasing it into the natural environment without a license is an offense

releasing or introducing fish into rivers, reservoirs and lakes is prohibitedSPMGRJSCconfirm with the agency

Introducing an exotic species, or one outside its natural range, without a technical opinion and a license is a federal environmental offense. This includes releasing a fish from a tank, pay lake or aquarium into a river or reservoir. In MG, the IEF states that stocking without a license is prohibited.

Source: Lei federal nº 9.605/1998, art. 31, and Decreto federal nº 6.514/2008, art. 25

catch and release
catch and release Releasing the fish alive, quickly and with a wet hand. During a closed season it isn't always allowed: what the regulation says applies.

Wet hands, fish kept in the water, barbless hook. Don't squeeze, and don't take it out of the water on a hot day.

in the kitchen

Pink, delicate meat; grilled in butter, with almonds or smoked.

calculator

how much it weighs without taking it out of the water

Length-weight relationship W = a·Lb (a = 0.00933, b = 3.03; FishBase). It's an average: a fat or lean fish can vary by 10% to 20%.

estimated weight

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sources and references

The season weights (months), the time of day and the sensitivities (cold, pressure, moon, wind, rain, tide, strong light, murky water and noise) are the app's editorial estimates, based on the literature below and on the field experience of anglers and guides. They are not official data nor a measurement made for this species, and they may vary by region and year. Closed seasons and legal rules appear in the rules section, with the norm and a link.

  1. scientific FishBase — Oncorhynchus mykiss (ficha da espécie)Names, distribution, biology, length-weight relationship and references. Page checked on October 13, 2026.
  2. scientific IUCN Red List — Oncorhynchus mykiss (avaliação global: Pouco Preocupante, LC, 28/07/2020)Global assessment. Link given on the FishBase entry (Red List, version 2025-2).
  3. technical CABI Compendium — Oncorhynchus mykiss (rainbow trout). Rojas-Sandoval, J. (2024).Technical sheet for an invasive species (DOI checked in Crossref).
  4. scientific IUCN SSC Invasive Species Specialist Group — Global Invasive Species Database: Oncorhynchus mykissPage checked on Oct 13, 2026.