Illinois-Indiana Sea Grant | University of Illinois

Back to Newsroom

FOR IMMEDIATE RELEASE
June 18, 1998

New Invader May be Headed for Lake Michigan

A new invader, Daphnia lumholtzi, may soon join other nonindigenous species in Lake Michigan. According to Jim Stoeckel, Daphnia lumholtzi provides a classic example of the continuing need to control entry of nonindigenous species as addressed by the Nonindigenous Species Act of 1990 (NISA), amended in 1996. Stoeckel, an Illinois Natural History Survey (INHS) aquatic biologist, has been monitoring movement of this newest invader since 1995 as it makes its way toward Lake Michigan.

This new invasion is a quiet one compared to the now well known zebra mussel invasion. "Daphnia lumholtzi doesn't shut down power plants, and few people besides biologists even know about it," Stoeckel said. Daphnia lumholtzi does, however, represent an ecological threat that could negatively affect sport and food fish.

Daphnia lumholtzi is a type of zooplankton commonly known as a water flea (no relation to fleas around dogs or cats), with sharp spines protruding from its body. Large individuals can reach about one-quarter inch in length. "The spines make them less susceptible to predators than native Daphnia, which are important food sources for young fish," Stoeckel said.

"If Daphnia lumholtzi begin to replace native Daphnia species, the food supply for young fish will be reduced. If Daphnia lumholtzi becomes established in hatchery ponds, similar problems are expected. At the present time, however, population abundances of Daphnia lumholtzi peak during the hot summer months when populations of native Daphnia are often low anyway. By mid-summer, young-of-year of many fish species have grown large enough to feed on prey items other than zooplankton. The ultimate effect of this invader, therefore, is far from certain."

Daphnia lumholtzi was first documented in the Illinois River in 1995 approximately 135 river miles south of Lake Michigan during INHS monitoring for zebra mussels. By 1996, it was found in Cal-Sag Channel, only 30 miles from Lake Michigan. Stoeckel said, "Samples collected by INHS in 1997 are being analyzed to determine whether the Lake Michigan invasion is already underway."

Although adult Daphnia lumholtzi can be controlled through traditional chemical and heat control methods, eliminating them is next to impossible. Daphnia lumholtzi produce resting eggs which are coated in a protective covering called an ephippium. This coating permits eggs to survive outside the water allowing for movement by wind, waterfowl and other methods. These resting eggs may remain dormant for decades before hatching.

Native to Africa, Asia and Australia, Daphnia lumholtzi was first reported in the United States in an East Texas reservoir in 1991. The reservoir had been stocked in the 1980s with at least two species of African fish, tilapia and Nile perch. Daphnia lumholtzi was later found in samples collected from Missouri reservoirs as far back as 1990. According to Stoeckel, the species probably came to North America with Nile perch but may have been introduced through the aquarium trade.

The Illinois River and connected, man-made waterways provide direct access to Lake Michigan from where species can quickly spread throughout the Great Lakes and other northern inland rivers and lakes. Stoeckel noted, "One of the projects funded by NISA is the creation of the dispersal barrier between Lake Michigan and Illinois waters in the Chicago Sanitary and Ship Canal to help prevent the spread of unwanted organisms. No single control method will be 100 percent effective. Our best bet is to implement a combination of control strategies to limit the introduction of invasive species to North America and to slow their rate of spread once invaders arrive."

For More Information:
Stoeckel, J. A., L. Camlin, K. D. Blodgett, and R.E. Sparks. "Establishment of Daphnia lumholtzi (an Exotic Zooplankter) in the Illinois River," Journal of Freshwater Ecology, Volume 11, Number 3, September 1996

--30--

The Illinois-Indiana Sea Grant College Program is one of more than 30 National Sea Grant College Programs. Created by Congress in 1966, Sea Grant combines university, government, business and industry expertise to address coastal and Great Lakes needs. Funding is provided by the National Oceanic Atmospheric Administration (NOAA), U. S. Department of Commerce, the University of Illinois at Urbana-Champaign and Purdue University at West Lafayette, Indiana.