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RALEIGH, N.C. (March 23, 2005) — They resemble miniature lobsters but unlike their larger, ocean-dwelling cousins, they prefer freshwater. Whether they’re burrowing in the mud, cowering under a rock or hiding among roots or leaf litter, crayfish inhabit almost any freshwater habitat in North Carolina, from small mountain streams and wet fields to large lakes and rivers. And while most people’s experience with them is limited to the home aquarium or the occasional pot of steaming gumbo, crayfish serve significant ecological and economic roles that belie their diminutive size.
They serve as a vital link in the aquatic food chain by feeding on both living and dead plants and animals. In turn, they are consumed by a large number of aquatic and terrestrial animals, including fish, reptiles, amphibians, wading birds, raccoons, otters and other mammals. They are considered a delicacy, with millions harvested from commercial production ponds annually. And for serious anglers, they are the live bait of choice, proving irresistible to a number of prized game fishes, including trout, largemouth bass and smallmouth bass. As important as crayfish are to the entire aquatic ecosystem, relatively little is known about these secretive aquatic creatures. To learn more about stream-dwelling and burrowing crayfish in western North Carolina, biologists with the N.C. Wildlife Resources Commission are surveying crayfish populations this spring. Biologists are conducting the survey in the Little Tennessee, French Broad, Watauga, Hiwassee, Savannah, New, Catawba and Broad river basins to determine how crayfish species are distributed, to monitor populations over time and to identify previously unknown populations—including introduced, non-native species. This survey, which started in 2004, is the latest component of an ongoing effort that began in the late 1990s to inventory and monitor crayfishes across the state. “Surveys such as this one are how we determine the distribution and abundance of crayfish in North Carolina,” said Steve Fraley, aquatic nongame coordinator for the Wildlife Commission. “Because we have limited historical data with which to compare current distributions, it is hard to determine how land-use practices and other effects of human actions, such as introductions of non-native crayfishes, have affected native crayfish populations in North Carolina.” From previous surveys, biologists have found that crayfish, like most aquatic species, can suffer when water and habitat quality decline. “Habitat degradation through dredging and damming waterways or
land-use practices, such as logging and development, can result in decreased
habitat and food available to crayfish,” said Jeff Simmons, an
aquatic nongame biologist with the Wildlife Commission. “Likewise,
changes in water quality due to sewage or agricultural and urban runoff
can be detrimental to crayfish populations as well as to animal populations
that consume crayfish.” “Non-native crayfish introductions threaten native crayfish species, often outcompeting them for food and displacing them from their preferred habitats,” Simmons said. “Crayfish species that are found only in a few places, such as many species in the western mountains, are especially vulnerable to these invasions.” Protecting native crayfish is a concern for biologists because native species are adapted to the habitats and communities in which they are found, and they play a vital role in maintaining a balanced ecosystem. Introduced crayfish can impact fish populations as well by preying on young fish, forcing them out of their habitats, altering habitats or disrupting food chains. Often, non-native crayfish introductions happen when anglers, using crayfish for bait, release them into public waters. Other introductions happen when crayfish escape from commercial production ponds. “Whether bait crayfish are collected from the wild or are bought from a bait shop, they should never be released into waters from which they were not collected originally,” Fraley said. “Unused bait crayfish should be destroyed, kept in a closed container to prevent escape until the next fishing trip or returned to where they were collected.” The consequences of non-native crayfish introductions are serious enough that the Wildlife Commission recently passed a regulation to ban possession of two particularly invasive and destructive crayfish species, the virile crayfish and rusty crayfish. Introduced in North Carolina’s waters presumably through bait-bucket releases, these two species are aggressive competitors with native crayfish and are destructive to aquatic plants, which can deprive native fishes and their prey of food and cover. “Because these impacts are gradual, anglers may not see effects of non-native crayfish introductions until the damage is done,” Simmons said. In the United States and Canada, there are currently 350 recognized crayfish species, with the greatest diversity of these species in the Southeast. There are more than 40 species that call North Carolina’s waters home, including at least 13 species that are found only in North Carolina, and three introduced species that are native to other parts of the U.S. but not native to the state. “Crayfish are an important part of our state’s diverse native wildlife heritage,” Simmons said. “Projects like this survey will enable us to learn as much about their populations as possible so that we can ensure their survival for future generations to enjoy.” North Carolinians can support the state’s research and management of crayfish and other nongame species through the Tax Check-off for Nongame and Endangered Wildlife, which allows taxpayers to designate part or all of their state tax refunds to benefit wildlife. Since 1984, taxpayers have given more than $7 million for wildlife conservation through the Nongame and Endangered Wildlife Fund. For more information on the crayfishes of North Carolina, visit "NC Crayfishes: Life at the Bottom". |
