Virile Crayfish (Faxonius virilis)
Species at a Glance
The Virile Crayfish, also known as the Northern Crayfish, is considered one of the most widespread invasive crayfish species in the United States. Its popularity as a live bait species has likely contributed to its spread through bait bucket release. Its large size, adaptability, and high reproductive capacity has made the Virile Crayfish a significant threat to native crayfish species and local ecosystems.
Species Description
The Virile Crayfish has a smooth body that can vary in color from light- to olive-brown, with paired dark brown blotches running lengthwise along the abdomen. The claws, called chelae, are typically green to blue-green with orange tips. In adults, the chelae are prominently covered with whitish or yellowish bumps. The upper walking legs are also bluish in color. The rostrum, which is the pointed nose-like structure between the eyes, has conspicuous notches or spines near its tip. Adult Virile Crayfish can reach a size of 45–125 mm (2 to 5 inches), with males usually growing larger than females.
Native & Introduced Ranges
Although native to parts of the United States, including the Great Lakes, Missouri River, upper Mississippi River, lower Ohio River, and areas east of the Continental Divide in Montana, the Virile Crayfish is considered invasive in several states outside its native range, including Maryland, North Carolina, Pennsylvania, West Virginia, and Virginia. In Pennsylvania, the Virile Crayfish has been reported primarily in the eastern portion of the state.
Biology & Spread
The Virile Crayfish has spread largely due to its popularity as bait and was most likely introduced outside of its native range through bait bucket release. It may also have escaped during intentional stocking as forage for frog and fish farms.
Habitat
A habitat generalist, the Virile Crayfish can be found in a range of flowing or still waters such as streams, rivers, canals, ponds, and lakes. While this species cannot colonize fast-flowing streams, it can tolerate high turbidity and is often found in habitats with abundant plant cover and muddy, sandy, or rocky substrates. It is also considered a burrower that can move from pond to pond. While the Virile Crayfish prefers warmer temperatures, it has been documented to have a wide range of thermal tolerance between 0—18⁰C (32—64.4 ⁰F) and has been known to survive in very cold waters during the winter.
Impacts:
Threat to Biodiversity
The Virile Crayfish can significantly alter aquatic ecosystems by reducing native plant growth, disturbing macroinvertebrate communities, and increasing water turbidity. Its feeding and burrowing behaviors decrease biodiversity, displace native crayfish, reduce snail populations, and alter the structure of aquatic habitats. It also feeds on fish eggs and competes with native fish for food and shelter, contributing to declines in fish populations. High densities of Virile Crayfish have been linked to reduced native fish and macroinvertebrate populations, while also facilitating the spread of invasive predatory fish, further threatening native species.
Sources:
Durland Donahou, A., 2025, Faxonius virilis (Hagen, 1870): U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL
Missouri Department of Conservation. Virile Crayfish. Field Guide
U.S. Fish and Wildlife Service. 2015. Virile Crayfish Ecological Risk Screening Summary
