Invasive crayfish threatening to infest Little Juniata River
By Mark Nale Northcentral correspondent
Alexandria, Pa. — On a recent trip to the Juniata River near
Petersburg, Huntingdon County, Bill Anderson discovered a large
number of unusual-looking crayfish inhabiting the river.
The crayfish, thousands of them, were concentrated just below
the hydroelectric dam at Warrior Ridge, south of Petersburg.
Anderson, president of the Little Juniata River Association,
suspected that the crayfish were rusty crayfish, a destructive
invasive species that is not known to live above the dam. He
contacted crayfish researcher David Lieb, who is currently working
in nearby Spruce Creek.
Lieb’s crayfish research in central Pennsylvania streams is part
of his pursuit of a doctoral degree in ecology at Penn State. He
positively identified Anderson’s crayfish as a rusty.
According to Lieb, rusty crayfish can be recognized by the rust-
or maroon-colored splotches that are found on both sides of the
crustacean’s midsection. The spots are located at the exact point
where your fingers would hold a crayfish so they won’t get
The large black-tipped claws of the rusty crayfish often take on
a blue or bluish-green color on older crayfish. They have a high
rate of reproduction, grow fast and can get up to 6 inches long —
almost small lobster-sized. They are native only to streams and
lakes in Indiana, Ohio and Kentucky.
Rusty crayfish have been accidentally introduced into
Pennsylvania, New York, Maryland, West Virginia and at least 13
other states, mostly in New England and the Midwest.
The usual method of introduction is by anglers using them as
bait. Here in Pennsylvania, rusty crayfish are believed to be
firmly established in the Ohio River Basin, as well as the Juniata
and lower Susquehanna rivers.
Being aggressive, rusty crayfish displace native species. “In
Penn-sylvania, they’ve come in and absolutely wiped out the native
crayfish populations,” said Lieb. “In my research, I don’t think
that I’ve ever discovered another crayfish species in a stream
where rusties have invaded.”
In the end, this could result in less food for fish. Rusty
crayfish are not as high-quality food as the invertebrates that
they replace. “It is not that rusties aren’t eaten by fish, but I
think that they grow so quickly that they grow past that small
vulnerable stage in a short time,” Lieb said.
When introduced, rusty crayfish also reduce aquatic plant
abundance and species diversity, according to Lieb. This can be
especially damaging in relatively unproductive northern lakes,
where beds of aquatic plants are not abundant. Submerged aquatic
plants are important in these systems as habitat for invertebrates
(which provide food for fish and ducks), shelter for young gamefish
or forage species of fish, and nesting areas used by fish.
Anderson has contacted the Pennsylvania Fish & Boat
Commission to alert it of the potential problem and to ask them to
take measures to stop the continued spread of rusty crayfish. He
was under-whelmed by the agency’s response.
“Recognizing the problem, several states have banned the sale
and use of all crayfish as bait and started an education program –
I suggested that the Fish & Boat Commission do the same,” said
In a reply to Anderson, Chief of Fisheries for the commission,
Rickalon Hoopes, wrote, “Sales of rusty crayfish, Orconectes
rusticus, are not permitted in Pennsylvania as defined by the
approved species list provided to the Department of Agriculture,
the agency that registers and regulates bait fish and fish bait in
“Banning the sale of all crayfish and banning the use of all
crayfish would certainly be a gesture, but such an approach would
need to be reviewed by staff for effectiveness and discussed with
the Department of Agriculture or the Aquaculture Advisory
Commit-tee,” Hoopes wrote.
In a phone interview, Hoopes indicated that agency staff was
meeting on Sept. 30 to discuss the entire invasive species issue,
but he gave no assurances that any recommendations about rusty
crayfish would be made to the commissioners at their next
“The cat is already out of the bag, so controlling rusty
crayfish will be a challenge. Other than a symbolic gesture, I’m
not sure what we can do,” Hoopes said.
Commission press secretary Dan Tredinnick said, “We don’t know a
whole heck of a lot about Pennsylvania crayfish. We are waiting to
get back the data from the crayfish population and diversity study.
Then we can decide what we might do.”
With rusty crayfish in abundance just below the Petersburg Dam
and only a stone’s throw away from invading the entire Little
Juniata watershed, including Spruce Creek and many other stocked
and Class A trout streams, Anderson doesn’t want to wait.
Lieb is a little more patient. “I’ve made commission officials
aware of the problem and I think that they will act. It just takes
time,” he said.
“The public needs to know that when they collect crayfish from
one part of a stream and move them to a different stream, or in the
case of the Little Juniata River, a tributary of the same stream,
that it is an extremely bad idea,” Lieb said. “An education effort
combined with banning the sale of all crayfish would stop 90
percent of rusty crayfish introductions to new waters. Banning all
use of crayfish as bait is also a very good idea.”