Coho salmon

Quick facts

Adult size

60 cm, 4500 g typical harvest weight

Days to harvest

365 to 730 days from fingerling

Lifespan (max)

up to 5 years

Diet

carnivore

Temperature class

cold-water

Difficulty

advanced

Water parameters

Temperature range

4–16°C (optimum 12°C)

pH

6.5 to 8

Hardness

3 to 18 dGH

Minimum tank

2000 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)

0.70% of body weight per day

Max stocking density

40 g per litre of system water

A 4500g adult eats about 54.0 g of feed per day at optimum temperature. For a roster of 10 fish at adult size, that's around 540 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 Pacific coast rivers and streams from central California north through Alaska and across to Japan and eastern Russia. The species (Oncorhynchus kisutch) is an anadromous Pacific salmon that rears in freshwater streams for 1-2 years as juveniles before migrating to the ocean, returning to spawn after 1-3 years at sea. Also called silver salmon for the bright metallic sheen of ocean-phase fish. Coho are medium-sized among Pacific salmon: adults typically weigh 3–6 kg. The flesh is orange-red, moderately fatty, firm, and well-flavored, considered second only to chinook in quality among Pacific salmon. Wild coho populations have declined significantly in many river systems; several runs in the Pacific Northwest are ESA-listed as threatened or endangered. Coho aquaculture is a significant industry in Chile (the world's second-largest salmon producer) and Japan, producing several hundred thousand tonnes annually from marine net-pen operations.

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 species with limited applicability to freshwater aquaponics, included for reference and completeness. Coho salmon require cold water (8–14°C) and high dissolved oxygen (above 7 mg/L). The juvenile freshwater phase (parr to smolt) takes 12-18 months, producing a fish of 10–30 g before the animal naturally wants to migrate to saltwater. Growing coho to market size (2–4 kg) entirely in freshwater is done in some Chilean and Japanese recirculating operations but requires sophisticated system management. FCR in culture is 1.2-1.5 on salmon pellet (40-48% protein). Stocking density in RAS: 30-50 g/L with supplemental oxygenation. For practical freshwater aquaponics, rainbow trout or arctic char are better choices because they grow well in fresh water for their entire life cycle without the physiological stress of suppressing a species programmed to migrate to the ocean. Coho fingerlings are available from some Pacific Northwest hatcheries, but conservation regulations restrict their sale in many areas. Legal status depends on stock origin (wild-derived vs. domesticated) and varies by state and province. Disease concerns include bacterial kidney disease, vibriosis, and IHN virus, all common in salmon culture. Not recommended for home aquaponics.

Further reading

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