How to Identify Rusty Crayfish

To identify Rusty Crayfish (Faxonius rusticus), look at these key features.

Physical Characteristics

Body shape

elongated

Coloration

Typically olive-green to reddish-brown, with two distinct rust-colored spots on the sides of the carapace, just anterior to the tail. The underside is usually lighter. Claws often have black bands near the tips.

Scale type

none

Mouth position

inferior

Distinctive features

Two prominent, reddish-brown (rusty) spots on the carapace, one on each side., Large, robust claws (chelae) with black bands near the tips., Rostrum (forward projection of the carapace) is typically smooth and lacks spines on the margins., Chelae are often smooth or only slightly tuberculate.

Dorsal fin

Not applicable (crustacean)

Tail fin

Telson and uropods form a fan-like tail for propulsion (not true fins)

Pectoral fin

Not applicable (crustacean)

Distinctive fins

The telson is typically triangular with a rounded posterior margin.

Identification Tips

1. 1

   Rusty Spots

   Look for the two distinct, reddish-brown spots on the sides of the carapace. These are the most reliable identifying feature.

2. 2

   Claw Markings

   Observe the claws for black bands near the tips. This is a common, though not exclusive, characteristic.

3. 3

   Rostrum Shape

   Examine the rostrum; it is typically smooth-margined without prominent spines, distinguishing it from some native species.

4. 4

   Size

   Adults can reach a carapace length of 4-5 cm (1.6-2 inches) and a total length of up to 10-12 cm (4-5 inches), making them relatively large among North American crayfish.

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