Characteristics: (University of WI Limnologist) The Eurasian spiny water flea (Bythotrephes longimanus) is a large (2 cm) freshwater zooplankton native to northern Europe and the Caspian Sea. The crustacean is named for the large, barbed terminal spine (up to 70% of its body length) which is thought to deter fish predators. Bythotrephes arrived in North America around 1982 in Lake Ontario, possibly accompanying ballast water of an oceanic freighter. Following their arrival in Lake Ontario, spiny water fleas spread to each of the remaining Great Lakes by 1987. From there, they have made their way into inland lakes in Ontario, Michigan, Minnesota, Ohio, and, most recently, Wisconsin. On September 6, 2003, the spiny water flea was discovered for the first time in an inland lake within Wisconsin in the Gile Flowage, an impoundment in Iron County.
Spiny water fleas are predatory, and therefore consume many types of native zooplankton that occur within a lake. In Harp Lake, Ontario, Dr. Norman Yan and colleagues found that spiny water fleas caused rapid and substantial declines in native zooplankton species richness. Based on long-term data from one lake, these effects appear to be prolonged. Consequently, it has been suggested that spiny water fleas reduce the availability of smaller zooplankton for juvenile fish to consume. Owing to their large size and spine, Bythotrephes are relatively unpalatable to many smaller fishes. This suggests that Bythotrephes could have negative impacts on fish growth and survivorship by competing with them for food.
(Cornell Cooperative Extension of Cayuga County, NY) More commonly referred to as the Spiny Water Flea, this creature is in fact a crustacean that in certain aspects resembles a tiny shrimp. The origin of the Spiny Water Flea is Britain and Northern European nations. Before long, the crustacean found its way west by catching a ride in the ballast water of an ocean freighter. It was found in Lake Huron during the 1980s and continued to reproduce rapidly. Today it inhabits all the Great Lakes and about 80 other inland lakes of North America. The Spiny Water Flea is dangerous because it has great potential to disrupt the food web in our lakes. Their great populations may cause problems with other species, competing for food sources such as Daphnia (a small crustacean). Accompanied with their capacity to upset the food web, Spiny Water Flea#s have adapted extremely successfully to our environment. They reproduce at incredible rates, and the female's eggs can survive passing through the intestinal systems of birds or fish, while hatching increases in chlorinated waters. In favorable conditions they reproduce sexually, and in unfavorable conditions they have the ability to reproduce asexually, with eggs that remain dormant. That isn't even the bad news. The area in which they reproduce, the thermocline is increasing. This is the area between surface water and deep water where temperatures transition, its increase may be due to global warming. Here the Spiny Water Flea is invisible to predators, but can still reproduce. As a non-native invasive creature, the Spiny Water Flea has no natural predators to keep its population in check. If they were being consumed their presence would be less troublesome. One of the adaptations to avoid predation is their long sharp spine they are named for. It has been known to pierce the guts of fish or deter predators from attempting to swallow them at all.
Life cycle: (University of WI Limnologist) Water fleas such as Bythotrephes are parthenogenetic, meaning they can alternate between asexual and sexual reproduction. During the summer, an individual female may produce numerous "cloned" offspring within 14 days. This has obvious and important ramifications for their ability to spread and multiply quickly within a newly colonized system. Spiny water fleas can also reproduce sexually, generating resting eggs that may lie dormant for extended periods.
According to Craig Roesler, WDNR Water Resources Management Specialist, Hayward, in a presentation on 20, 2006 as part of "An Evening With Aquatic Invasive Species Researchers", Spiny water fleas will not survive in water temperatures greater than 77 degrees farenheit.
Methods of prevention: Live water fleas can be transported in boat live wells and bilge water while the fleas' resting eggs can become attached to fishing tackle, anchor lines, or mud clinging to boats or anchors. Through boat-mediated transport, it is suspected that spiny water fleas have been translocated to over 50 lakes in Ontario. Informational fliers advising lake users of the potential spread of spiny water fleas have been posted at each of Gile Flowage's boat landings and in local bait and boating stores. Boaters frequenting the Gile Flowage are strongly encouraged to drain their live wells, clean fishing gear and lines, power wash their boats, and/or allow their boat/equipment to dry for five days after use in the Gile.
Links to pdf documents
Pennsylvania Sea Grant
Indiana DNR
Links to other sites
University of Wisconsin Limnologist
Minnesota Sea Grant
Minnesota DNR
U.W. Madison 08/31/07 press release
Wisconsin DNR
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