Nature Lab

Fisheries Management

Monitoring Crayfish

Until a few decades ago, no one knew how crucial crayfish are to the food web. But when an MDC study revealed that crayfish make up 80 percent of the diet of rock bass and 75 percent of the diet of smallmouth bass, surveys were launched to dig deeper into crayfish biology.

“Crayfish aren’t just important to sport fish,” explains Research Biologist Bob DiStefano. “Across North America, more than 300 different species have been observed eating crayfish.”

Even bears and great horned owls eat them. Crayfish, in turn, eat many different things — insects, fish, plants, decaying wood and leaves, as well as microscopic plants and animals.

“Almost no other animal feeds at so many levels,” says DiStefano. But MDC’s surveys have uncovered more than crayfishes’ place in the food web.

“Before we started these studies,” says DiStefano, “a lot of people assumed that all crayfish species use the same types of habitats. But we found that’s not true. Crayfish are varied just like any other group of organisms.”

Some species need fast-flowing water, others slow. Some prefer standing water, some deeper water, some shallow. The type of stream bottom they prefer (rocky, muddy, sandy) can also vary from species to species. Even adult and juvenile crayfish use different parts of the same stream.

When DiStefano began this work in 1990, about 25 crayfish species were known to live in Missouri. Today that number is 38. Understanding the life history, abundance, distribution, and habitat needs of each is essential for effective management. MDC staff continue to unravel these details for more species, with a focus on species of conservation concern.

Missouri’s Crayfish at a Glance

By the Numbers

More than 400 species in North America

• 38 species in MO
• 30 species found in the Ozarks
• 27 species of conservation concern
• 8 species are endemic (found only in MO)

By Primary Habitat 

• Stream — 22 species
• Standing water (swamp, marsh, ponds, lakes) — 6 species
• Burrowing — 7 species
• Cave — 3 species

The longpincered crayfish is Missouri’s largest crayfish, growing to 6 inches or more in length.

Shufeldt’s dwarf crayfish rarely grows much longer than an inch.

Learn more at short.mdc.mo.gov/4Py