News from the DNR Office of Communications

DNR Study Confirms Threats To Native Crayfish

Annapolis, MD (April 26, 2010) — A new study by Maryland Department of Natural Resources (DNR) biologists finds that several of Maryland’s native crayfish species have declined due to the introduction and spread of invasive species. This new study highlights the need for increased public awareness of invasive species issues and public participation and support to prevent the spread of problem animals.

“It’s been over 45 years since the last comprehensive study of Maryland’s crayfish, and a lot has changed in that time” said Jay Kilian, a biologist in DNR’s Resource Assessment Service and one of the authors of the study. “Maryland is now home to five non-native crayfish, all introduced as unwanted pets, through their use as bait by anglers, or as a result of escapes from aquaculture operations.”

The threat looms large, especially with the first-ever discovery of the Rusty Crayfish, one of the most notorious invasive species, in three Maryland watersheds in 2007 and 2008.

Crayfish play important ecological roles in nature. They serve as prey to many terrestrial and aquatic predators and are important processors of organic matter, the basis of aquatic food webs. However, several non-native crayfish species have flourished, become invasive, and are now widespread in the state. These invasive species represent the greatest threat to Maryland’s 9 native crayfish species.

Invasive crayfish can become very abundant in the streams, rivers, and lakes in which they are introduced. They often out-compete native crayfish for shelter habitats and food. These invasive species can also reduce the quality and quantity of food and habitat available to other aquatic animals.

“The most important thing we can do to protect our native species is to prevent the further spread of invasive crayfish already in Maryland and keep other invasives out,” Kilian said.

The study’s results were recently published in a special issue of Southeastern Naturalist, the product of a scientific symposium on the conservation, biology, and natural history of crayfish from the southern United States. It is available online: For information about the DNR study, contact Jay Kilian (

   April 26, 2010

Contact: Josh Davidsburg
410-260-8002 office I 410-507-7526 cell

The Maryland Department of Natural Resources (DNR), which celebrated its 40th anniversary in 2009, is the state agency responsible for providing natural and living resource-related services to citizens and visitors. DNR manages more than 467,000 acres of public lands and 17,000 miles of waterways, along with Maryland's forests, fisheries, and wildlife for maximum environmental, economic and quality of life benefits. A national leader in land conservation, DNR-managed parks and natural, historic, and cultural resources attract 12 million visitors annually. DNR is the lead agency in Maryland's effort to restore the Chesapeake Bay, the state's number one environmental priority. Learn more at