Signal crayfish
Pacifastacus leniusculus
Water parameters
Minimum tank: 200 L per individual at harvest size.
Feed and growth
- Feed protein
- 30% target
- Daily feed (warm)
- 1.50% of body weight
- Daily feed (cool)
- 0.50% of body weight
- Max density
- 10 g per litre
A 120 g adult eats about 1.8 g of feed per day at optimum. 10 fish at adult size: ~18 g daily.
Legality
Rules vary by jurisdiction and change over time. Verify with your local fisheries or wildlife authority before stocking.
| Jurisdiction | Status | Notes |
|---|---|---|
| gb | permit required | Schedule 9 Wildlife and Countryside Act; keeping or releasing without licence is an offence verified 2026-05-14 |
| eu-general | restricted | EU Invasive Alien Species Regulation (1143/2014) lists signal crayfish; member states restrict import, trade, keeping, and release verified 2026-05-14 |
| Washington | legal | Native range; no restrictions on harvest or culture verified 2026-05-14 |
| Oregon | legal | Native range; commercially harvested verified 2026-05-14 |
Unlisted jurisdictions default to "check local regulations".
Origin and habitat
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
- temperate (handles seasonal swings)
- USDA zones
- 4–8 (winter low around -34°C or warmer)
- Heating needed
- no
- Cooling needed
- no
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.