Signal crayfish

Quick facts

Adult size

16 cm, 120 g typical harvest weight

Days to harvest

365 to 730 days from fingerling

Lifespan (max)

up to 20 years

Diet

omnivore

Temperature class

cool-water

Difficulty

intermediate

Water parameters

Temperature range

2–22°C (optimum 16°C)

pH

6.5 to 8.5

Hardness

5 to 20 dGH

Minimum tank

200 L per individual at harvest size

Feed and growth

Feed protein

30% target

Daily feed (warm water)

1.50% of body weight per day

Daily feed (cool water)

0.50% of body weight per day

Max stocking density

10 g per litre of system water

A 120g adult eats about 1.8 g of feed per day at optimum temperature. For a roster of 10 fish at adult size, that's around 18 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 freshwater rivers, streams, and lakes in the Pacific Northwest of North America, from British Columbia south through Washington, Oregon, and into northern California. The species (Pacifastacus leniusculus) was introduced to Europe in the 1960s as a replacement for native noble crayfish stocks decimated by crayfish plague. The introduction was catastrophic: signal crayfish are carriers of the Aphanomyces astaci plague pathogen (they're resistant to it) and their spread across Europe has caused the near-extinction of noble crayfish and other native European species. Signal crayfish are now established across Scandinavia, Britain, France, Germany, and much of Central Europe. Adults reach 15–20 cm and 80–200 g. The flesh is firm and sweet.

Climate and outdoor ponds

Climate classification

temperate (handles seasonal swings)

Outdoor pond zones (USDA)

4 to 8 (winter low around -34°C or warmer)

Heating in a temperate climate

Not required (handles seasonal cool periods)

Cooling in a temperate climate

Not required

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 temperate freshwater crayfish for aquaponics in cool-water systems (14–22°C optimal). Growth is moderate: 80–200 g in 12-18 months on crayfish pellet (28-35% protein). FCR is approximately 2.0-3.0. Stocking: 8-15 crayfish per square meter of bottom area. Signal crayfish are hardier and more aggressive than noble crayfish, which makes them easier to culture but also more destructive to other organisms in the system. They burrow aggressively (a serious concern in pond culture, where they can destabilize levees) and will eat small fish, worms, and plant roots. In aquaponics tanks, provide shelter structures and use solid-bottomed containers. The critical ethical and legal issue is disease transmission: signal crayfish carry crayfish plague and must never be kept anywhere near native European crayfish species. In Europe, signal crayfish are classified as invasive in many countries, and culture is either prohibited or strictly regulated. In their native Pacific Northwest range, they can be cultured without the disease concerns. Fingerlings are available from crayfish suppliers in the Pacific Northwest and (where legal) in Europe. For European aquaponics, noble crayfish or Astacus leptodactylus (Turkish crayfish) are the ethical native alternatives, despite their slower growth.

Further reading

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