WASHINGTON – Katelyn Horn gave up her afternoon, donned a pair of blue rubber Crocs and boarded a van for Taneytown Oct. 21 — all so she could spend a frigid few hours picking crustaceans out of the Monocacy River.
Horn, an environmental science student and sophomore at Hood College in Frederick, was one of eight students from the school to take part in an expedition headed by the Maryland Department of Natural Resources to capture invasive rusty crayfish in the river and take them back to the school to study their eating habits.
The DNR discovered about 800 of the non-native species in the northern portion of the Monocacy River last year during a routine stream survey. It soon determined that the breed, probably introduced to the Monocacy by anglers using it as bait, was more aggressive and faster-reproducing than other crayfish present in the river system — meaning it was competing with existing aquatic life for submerged aquatic vegetation, a food source.
Horn attributed the larger appetite of the invasive rusty crayfish to biological differences between it and other crayfish species in the Monocacy.
“They have a higher metabolism (so) they’re eating a lot of the food,” Horn said of the several-inches-long, brown crayfish that get their name from reddish spots on either side of their thoraxes.
Last Tuesday marked the launch of the DNR’s second year of invasive rusty crayfish research, an undertaking in which Hood College, Mount St. Mary’s University and the University of Maryland’s Appalachian Laboratory are all participating this year.
The goal of this year’s survey is to determine how far the species, a native of portions of the Ohio River, has spread since its discovery last year, said Jay Kilian, a biologist with the DNR.
“The population of Rusties is (so far) very similar to last year,” said Kilian, adding that, funding permitting, the DNR would like to continue the survey for another three years. “If they’re moving, it’s less than five kilometers a year. That’s a good sign — that means we have time (to contain them) before they reach the Potomac.”
The Monocacy is a tributary of the Potomac, which flows into the Chesapeake Bay and ultimately the Atlantic Ocean.
If the invasive rusty crayfish population were to go unchecked, it would affect fish populations in the Potomac, harming an iconic state pastime, said Ron Albaugh, the coastal studies coordinator at Hood.
“Recreational fishing would (suffer),” Albaugh said. “If the invasive rusty crayfish is competing for native food supply with bass and bluegill, (the fish’s) numbers would dwindle.”
The striped bass is a favorite Maryland fish, bringing thousands of anglers to the Chesapeake Bay each year.
Notices posted by the DNR have dotted telephone poles near fishing spots in the Monocacy since last year, reminding anglers never to dump unused bait into the water and that it is illegal to buy or transport the rusty crayfish.
“The fact is we really don’t know what the repercussions of having this species replace the others might be,” said Drew Ferrier, a biology professor at Hood College, as he stood in the water in hip-height rubber waders. “I think the most surprising thing is these are freshwater animals but they have the ability to tolerate … salinity and that may mean they’re able to spread (more easily).”
Invasive aquatic species are nothing new to Maryland. In 2002, for example, a northern snakehead fish, a species native to China that has no known predators and feeds almost entirely on other fish, was found in Crofton. Though it is illegal in Maryland to possess the northern snakehead, the fish continues to be ?a persisting problem? in the state?s waterways, said Olivia Campbell, a DNR spokeswoman.
The students and DNR staff members caught approximately 20 “Rusties” on Tuesday but they took just 11 — those that were full-grown — back to Hood to be studied, since adults tend to eat more submerged aquatic materials.
Ferrier and other Hood College faculty involved in the rusty crayfish study will present their findings at a Maryland Water Monitoring Council meeting in December.