Maryland Study Finds New Invasive Crayfish

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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.

“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.”  said Jay Kilian, a biologist in DNR’s Resource Assessment Service and one of the authors of the study.

The study found populations of the Rusty Crayfish in three Maryland watersheds in 2007 and 2008. The species was not previously known to exist in Maryland freshwater environments.

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 14 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:

This information is provided as a public service of the Maryland Department of Natural Resources.