Rusty Crayfish (Faxonius rusticus)
Key Identification Features
Rusty patch on carapace
Not always obvious after molt
Smooth, S-shaped dactyl
Oval gap when chelae closed
Tips of chelae are red-orange with black bands
Description
The rusty crayfish is an aggressive invasive in the New York region. They are aggressive both in invasive presence and personality type. Body length of an adult rusty crayfish averages about 10 cm, not including the claws. One key characteristic includes the rusty-colored oval patch on the sides of their bodies. The rest of the body is grey-green to red-brown. When their claws are shut there is an oval shaped gap between the top and bottom. The rostrum (tip of head area) is a good indicator between native and invasive crayfish species, as the rusty crayfish has one that is concave, pinched and smooth.
Native Range
The rusty crayfish is native to the Ohio River Basin in the Midwest. It has since spread in range to about 20 states and 2 Canadian provinces. Their expansion may be attributed to anglers use of them as bait.
Habitat and Dispersion
Rusty crayfish live in freshwater habitats such as lakes, rivers, streams, and ponds. They prefer to have debris present to hide under, like rocks or logs. They are very proficient invaders, as the females can carry up to 200 eggs at a time and the species easily outcompetes native crayfish due to their aggressive feeding behavior.
Best Management Practices
The best way to manage the spread of this species is to avoid using it as bait. Additionally, it is useful to clean watercraft and inspect for any living organisms that may be hitching a ride and then allowing the watercraft to dry before the next use.
In terms of land management, the encouragement of natural predators has been shown to help eliminate loosely established populations of rusty crayfish.