Invasive Species- The Rusty Crayfish

Because I introduced some vegetative invasive species in the dendrology post, I decided to look for a impending animal species to the watershed, one of which is the Rusty Crayfish.

Introduced as a bait fish for anglers, the rusty crayfish has established itself across the Monocacy watershed, out competes the native crayfish for habitat and food sources, severely impacts the submerged aquatic vegetation, and generally interrupts the food chain of  impacted waterways.  

Habitat:

The Rusty Crayfish is Native to the Ohio River basin in Ohio and Kentucky , prefers warms streams, flat rocks woody debris, and submerged aquatic vegetation. (SAV).  Opportunistic feeder but mostly focuses on benthic invertebrates, detritus, fish eggs, small fish and aquatic vegetation.

Have a denser shell than native species, which additionally removes them from the food chain rather than replace the crayfish that they push out.

Although the Rusty Crayfish prefers slow freshwater eddies, it has been found to be saltwater tolerant, which makes it a threat to the Potomac River and potentially the Chesapeake bay.  (MDNR, 2010)

Identification:

Reddish brown spot on posterior sides of carapace with a smooth, robust chela, and carapace.

Rostral margins with accessory spines.

The rusty had larger more robust claw than native species. 

Grow to a mature size of 3.5-10 cm and an average length of 6.4 cm (Sea Grant, 2016)

Invasive Characteristics:

·      Displaces native crayfish

·      Reduces the amount and variability of submerged aquatic vegetation

·      Decreases density and variety of invertebrates in the ecosystem

·      Reduces some fish populations due to changing the ecosystem.

There are currently no environmentally sound methods to eradicate the rusty crayfish. Best practice is to limit or slow their expansion.

Similar Species includes:

The native Spiny cheek Crayfish (orconectes limosus), and Alleganey ) Orconectes obscureus) and the virile crayfish (Orconectes virilis ),which is native to the Midwest and Northwest US. 

References

MDNR (2010),  An Invasion in Progress: The Spread of Rusty Crayfish in a Maryland Watershed, Maryland Department of the Environment, Accessed from : dbr2/.maryland.gov/streams/documents/rustycrayfishsurveyfactsheet.pdf

Swecker, C, Jones, T, Killian, J, Roberson, L, (2016), Key to the Crayfish of Maryland, DNR, Maryland Department of Natural Resources,  Key to the Crayfish of Maryland, Accessed from: dnr.maryland.gov/streams/documents/keytocrayfishesofMD.8_18_10.pdf

Seagrant, (2016) Rusty Crayfish: A nasty Invader, Biology, Identification, and Impacts, Accessed from: www.seagrant.umn.edu/ais/rustycrayfish_invader