What is the largest crayfish in North America?

The largest known North American crayfish is a Tennessee bottlebrush crayfish held in the Astacology Collection at West Liberty University in West Virginia. Collected in 2011 by Zac Loughman and West Liberty students, it measures 86.6 millimeters (about 3.4 inches) in body length, not counting its tail, claws, or antennae. The record comes from a study in the journal Ecology, reported on October 15, 2026, in which University of Illinois biologist Caitlin Bloomer and colleagues measured museum specimens nationwide and listed the 20 largest individuals, representing 18 species.

The researchers found that the biggest crayfish of most species topped out near 80 millimeters, and latitude, oxygen levels, and habitat type did not explain the differences. They suggest the limit may come from the animals’ own biology, such as exoskeleton or muscle structure, although that remains a hypothesis. Much larger crayfish exist elsewhere, including the Tasmanian giant freshwater crayfish.

Source: “‘Crawzilla’ was huge. Then scientists found an even bigger crayfish,” ScienceDaily, from materials provided by the College of ACES at the University of Illinois Urbana-Champaign (October 15, 2026).

Image: Big Sandy crayfish (Cambarus callainus), a related North American species. U.S. Fish and Wildlife Service Northeast Region, public domain, via Wikimedia Commons.