Since its introduction to Wisconsin waters sometime in the 1950s, the crayfish has spread to thousands of lakes and streams, clear cutting the underwater forests that are critical fish habitat, evicting the native crayfish from one body of water after another and scooping up fish eggs like so much caviar.
But the clawed invader, the early results of a long-term University of Wisconsin-Madison study suggest, may be vulnerable to a "double whammy" of intensive trapping and predator fish manipulation to the point where it may actually be possible to rid lakes of an animal that has vexed scientists, anglers and conservation agencies alike for decades.
"They pretty much wipe out all of the rooted aquatic plants, they eat fish eggs, they either eat or compete with native invertebrates and, in general, raise havoc with the near-shore community of a lake," says Stephen Carpenter, a UW-Madison professor of limnology and zoology involved in the study on Sparkling Lake in Vilas County, Wis.
Supported by the National Science Foundation (NSF), the long-term study of the feasibility of evicting the rusty from the 110-acre lake is now in its sixth year. It holds the promise of a rare victory in the war against introduced invasive species.
Since 2001, the UW-Madison researchers, aided by a small army of undergraduate students and the Wisconsin Department of Natural Resources (DNR), has succeeded in significantly reducing the population of rusty crayfish in Sparkling Lake through a program of intensive trapping and manipulating fishing regulations to favor the smallmouth and rock bass that dine on juvenile crayfish. The two-pronged attack, says Carpenter, has yielded very promising results.
"It seems to be working. The aquatic plants are back. That's good because that's fish habitat, and the fish populations are returning to what they were before the rusty got into the lake sometime in the 1980s," says Carpenter.
The two-pronged approach to ridding Sparkling Lake of its rusty crayfish is the key, notes Jake Vander Zanden, a UW-Madison professor of limnology who is helping oversee the experiment. "One important message is that trapping alone will not do it. There's a synergistic effect with the fish playing an important role."
Smallmouth bass and rock bass, says Vander Zanden, are the primary predators of juvenile crayfish, and to some degree sunfish - bluegills and pumpkinseeds - pitch in by eating the smallest crayfish. The Wisconsin DNR, by manipulating the bag and size limits for anglers fishing Sparkling Lake, has helped establish an optimal population of the fish that routinely dine on the crayfish.
The trapping on Sparkling Lake, however, has been intensive during six years with 280 traps seeded around the lake. Baited with beef liver, the traps snare both native and rusty crayfish, but the natives, Carpenter explains, are returned to the lake. The trapping targets the largest crayfish, those that may be too big for the lake's predators.
The big hope, says Carpenter, is that the experiment will expose a "tipping point," where the combination of trapping and pressure from predator fish pushes the rusty crayfish population to crash, with the lake ecosystem returning to its pre-rusty crayfish state.
"What we are wondering is whether we will reach a tipping point where the fish alone can keep up the pressure," says Carpenter, an authority on such ecological change. "We haven't seen it yet, but we're not prepared to admit there isn't a tipping point."
Vander Zanden says the rusty crayfish infestation in Sparkling Lake, like most lakes where it is found, was probably sparked by a small pioneer group that somehow got into the lake. At one time, rusty crayfish were used as bait. Misguided attempts years ago to establish the rusty in Wisconsin for commercial purposes also contributed to the spread of the exotic species to 50 percent of Wisconsin lakes and streams.
The practical upshot of the experiment and the real hope, say Vander Zanden and Carpenter, is that the experimental techniques used on Sparkling Lake can be transferred to other lakes with the help of the many lake associations in Wisconsin. The Wisconsin scientists have addressed lake associations and found a receptive audience.
"We have talked to lake associations," says Carpenter. "If everyone was willing to run half a dozen traps off their dock, it could be very effective."
And one of the best parts of the study, according to the Wisconsin scientists, is that the rusty crayfish is edible. "The students up at our Trout Lake Research Station have been eating a lot of crayfish," says Carpenter.
Stephen Carpenter | EurekAlert!
Joint research project on wastewater for reuse examines pond system in Namibia
19.12.2016 | Technische Universität Darmstadt
Scientists produce a new roadmap for guiding development & conservation in the Amazon
09.12.2016 | Wildlife Conservation Society
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.
The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...
UMD, NOAA collaboration demonstrates suitability of in-orbit datasets for weather satellite calibration
"Traffic and weather, together on the hour!" blasts your local radio station, while your smartphone knows the weather halfway across the world. A network of...
Fiber-reinforced plastics (FRP) are frequently used in the aeronautic and automobile industry. However, the repair of workpieces made of these composite materials is often less profitable than exchanging the part. In order to increase the lifetime of FRP parts and to make them more eco-efficient, the Laser Zentrum Hannover e.V. (LZH) and the Apodius GmbH want to combine a new measuring device for fiber layer orientation with an innovative laser-based repair process.
Defects in FRP pieces may be production or operation-related. Whether or not repair is cost-effective depends on the geometry of the defective area, the tools...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
16.01.2017 | Power and Electrical Engineering
16.01.2017 | Information Technology
16.01.2017 | Power and Electrical Engineering