It sounds like something from a 1950s horror film.
An alien species moves in and, slowly but insidiously, begins to take over. In time, it dominates the planet. Other species are wiped out.
What might be called Pennsylvania's “attack of the killer crayfish” isn't quite that bad, but it's serious enough that Pennsylvania Fish and Boat Commission officials will consider some changes to what kind of bait you can use.
The problem is that several invasive varieties of crayfish, most notably the rusty and virile, have been introduced into a number of waters, including the Susquehanna River, Spring Creek and Fisherman's Paradise.
Most native crayfish species exist at densities of one to two per square foot of stream bottom. Invasives populate streams at densities of 20 per square foot, said Dave Lieb, invertebrate zoologist in the Pennsylvania Fish and Boat Commission's natural diversity section.
That's bad not only for the native crayfish they displace, but also the plants, aquatic insects and fish eggs they eat, and even the fish, birds and mammals that might try to prey on them, he said. Invasive crayfish eat more, grow faster, and quickly become too large to be prey. That leads to fewer, and slower growing, fish.
“The bottom line is you end up with lots of exotic crayfish and less of just about everything else,” Lieb said.
Invasives are hard to remove once they become established, so preventing them from spreading is the key, he said. The good news is the only way they get from one water to another is via people.
“It's not all gloom and doom in this state in that there's time to do something about it,” Lieb said.
What commission staff will propose is banning the possession, sale and transportation of all species of crayfish unless the head has been removed behind the eyes.
Bob Frye is a staff writer for Trib Total Media. Reach him at firstname.lastname@example.org or via Twitter @bobfryeoutdoors.
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