Marbled Crayfish and Rusty Crayfish

Table of contents:

• Aquatic invaders
• Pathways of invasion
• Threats to the environment, the economy and society
• Focus on an invader
• What you can do

• What to do if you find aquatic invasive species?

Marbled Crayfish

(Procambarus virginalis)

Characteristics

• generally less than 10 cm, can be up to 13 cm
• narrow pincers, like claws
• brown or green mottling on the shell, darker on wild individuals and lighter on captive individuals

Origin

Marbled Crayfish, also known as Marmorkreb, is a freshwater crustacean that resembles a small lobster. It belongs to the order Decapoda (ten legs). It is thought to have originated from captive breeding, therefore, it is not indigenous to any territory. First reported in 1995, it was introduced voluntarily to Madagascar for food. It is now found in several European countries and in Japan. Marbled Crayfish is a concern because it is presently available for sale (food, live bait and aquarium trade). The first report of this crayfish in the wild in North America was in 2023, in an Ontario pond.

Habitat

Due to its ability to adapt to weak or strong currents, Marbled Crayfish can live in ponds, streams, and lakes as well as in rivers. Optimal water temperature for this species is around 20°C, but the species has now adapted to the cooler waters of temperate zones. During a drought, it can also survive out of water for up to three days.

Similar species

It is easy to confuse Marbled Crayfish with native species such as Spinycheek Crayfish (Faxonius limosus). However, the mottling on the carapace of Marbled Crayfish can be used to distinguish it from native crayfish. It also resembles the Calico Crayfish (Faxonius immunis), a crayfish native to Ontario, but introduced to Quebec.

Spinycheek Crayfish

Rusty Crayfish

(Faxonius rusticus)

Characteristics

• between 7.5 cm and 13 cm
• black bands at the tips of the claws and oval gap when closed
• rusty patches on each side of the shell (near the tail)
• colour of the shell varies between a grey-blue and a dark brown-greenish

Origin

Rusty Crayfish is a freshwater crustacean that resembles a small lobster and belongs to the order Decapoda (ten legs). This invasive species is native to the Ohio River basin in the United States. It is believed to have been spread by either live-bait for recreational fishing or via the aquarium trade. It was first observed in Ontario in the early 1960s. In Quebec, it was present in the Outaouais region in the early 2000s. It has since also been observed in the Laurentides and Estrie regions.

Habitat

Due to its ability to adapt to weak or strong currents, Rusty Crayfish can live in ponds, streams, and lakes as well as in rivers. It prefers bottoms strewn with rocks, gravel and objects that form shelters. It can also be seen on sandy or loamy bottoms and in areas covered with aquatic plants. This species can tolerate a large range of temperature (0°C to 39°C).

Similar species

Several species of crayfish look alike, and it is easy to confuse Rusty Crayfish with native crayfish species. It particularly resembles two crayfish, Virile Crayfish (Faxonius virilis) and Northern Clearwater Crayfish (Faxonius propinquus). Besides the rusty patches on its body, Rusty Crayfish is larger than the others and its claws have black tips.

Virile Crayfish