Brown trout

Quick facts

Adult size

50 cm, 1500 g typical harvest weight

Days to harvest

540 to 730 days from fingerling

Lifespan (max)

up to 20 years

Diet

carnivore

Temperature class

cold-water

Difficulty

intermediate

Water parameters

Temperature range

3–20°C (optimum 16°C)

pH

6.5 to 8

Hardness

3 to 20 dGH

Minimum tank

500 L per individual at harvest size

Feed and growth

Feed protein

45% target

Daily feed (warm water)

1.20% of body weight per day

Daily feed (cool water)

0.80% of body weight per day

Max stocking density

35 g per litre of system water

A 1500g adult eats about 18.0 g of feed per day at optimum temperature. For a roster of 10 fish at adult size, that's around 180 g of feed daily.

Legality

Aquaculture and possession rules vary by jurisdiction and change over time. This table reflects regulations as of the verified date on each row. Verify with your local fisheries or wildlife authority before stocking.

Jurisdictions not listed here default to "check local regulations". A non-listing is not a green light; rules in your specific county or municipality may apply.

Habitat and origin

Native to Europe, from Iceland and Scandinavia south to the Atlas Mountains of North Africa and east through Turkey to the Caspian basin. The species (Salmo trutta) is one of the most widely introduced freshwater fish in the world, now established on every continent except Antarctica. Brown trout are found in cold, well-oxygenated rivers and lakes. They're closely related to Atlantic salmon (same genus, Salmo) and share similar habitat requirements. Brown trout are arguably the most culturally important freshwater fish in Europe, central to the fly-fishing tradition and to regional cuisines from Scandinavia to the Mediterranean. The flesh is white to pink, firm, and well-flavored. Brown trout aquaculture is established primarily in Europe and is smaller in scale than rainbow trout farming.

Climate and outdoor ponds

Climate classification

cold-water (cool water required, dies in heat)

Outdoor pond zones (USDA)

3 to 7 (winter low around -40°C or warmer)

Heating in a temperate climate

Not required (handles seasonal cool periods)

Cooling in a temperate climate

Required if your summer water temperatures exceed the upper tolerance

Zone bounds reflect year-round outdoor pond viability with no active heating. Anywhere outside the bounded zone, the species can still be kept in an indoor heated tank or a seasonally-managed system. Verify your specific microclimate, as a sheltered yard zone can run a half-zone warmer than the regional rating.

Care notes

A cold-water aquaponics species with characteristics between rainbow trout and brook trout. Optimal temperature is 12–18°C, with tolerance up to about 24°C (slightly warmer than brook trout, slightly cooler than rainbow trout). Growth: 300–500 g in 14-20 months on salmonid pellet (40-45% protein). FCR is 1.2-1.5, comparable to rainbow trout. Brown trout are notably more aggressive and territorial than rainbow trout, which affects stocking density: keep at 15-25 g/L, and provide structure (pipe sections, shaded areas) to reduce territorial disputes. They're also harder to train to pelleted feed than rainbow trout; source fingerlings that have been weaned onto pellets early. Dissolved oxygen above 6 mg/L; ammonia below 1 mg/L. Brown trout are more disease-resistant than rainbow trout in some contexts, particularly against whirling disease (Myxobolus cerebralis), which devastates rainbow trout populations but affects brown trout less severely. Fingerlings are available from trout hatcheries, primarily in the eastern US and Europe. Legal in most jurisdictions where trout culture is permitted. Brown trout are the best choice for aquaponics operators in Europe who want a native cold-water species, and a reasonable alternative to rainbow trout in North American cold-water systems.

Further reading

• Aquaponics water chemistry: balancing pH for fish and plants
• Fish for aquaponics: tilapia vs everything else