Spiny waterflea (Bythotrephes longimanus) are a microscopic freshwater zooplankton that invade lakes and can take over the bottom of the food chain, disturbing the ecology of the lake and presenting a serious potential threat to Minnesota lakes. They can decimate populations of Daphnia and other native zooplankton resulting in a decreased food source for native fish and an increase in algal blooms. They can also clog the eyelets of fishing rods, causing problems for recreationalists.
At their peak, their populations reproduce rapidly and can be as high as 100 individuals per cubic meter, sometimes taking over the biomass of the lake. There are fewer predators on spiny waterflea than on native zooplankton because small or young native fish can’t consume their sharp, barbed spine.
Because it is not yet well understood how their establishment and proliferation translates into impacts on native game fish, MAISRC researchers are using paleolimnology data to more fully identify the long-term impacts of spiny waterflea. Click here to download a factsheet about spiny waterflea.
About spiny waterflea
What they look like
Spiny waterflea is a member of the Crustacea, a large taxonomic group that includes crayfish, shrimp, and crabs. Adult spiny waterfleas grow to be about one centimeter long. They have a single long tail with multiple barbs which helps them avoid predation. When they are grouped together, as ensnared on fishing lines and cables, they collect and form gelatinous globs.
Part of spiny waterfleas’ success is due to their ability to reproduce rapidly – they can mature and reproduce within about one week. They can reproduce both asexually and sexually. Females can produce up to 10 young every two weeks without mating. In the fall, males and females reproduce sexually and produce resting eggs that settle in lake sediments, where they overwinter in a dormant state. These resting eggs are resistant to short-term drying (up to 4 hours) when out of the water and can establish a new infestation in a different lake.
In adulthood, they prefer cooler water and are generalist predators, meaning they are able to feed on a broad range of prey.
Where they’re found
Spiny waterflea are native to Europe and Asia. They were first found in Lake Superior in 1987 and first discovered in inland Minnesota lakes in Island Lake Reservoir north of Duluth in 1990. Today, they are found in Lake Mille Lacs, Lake of the Woods, and Lake Vermilion. As of 2015, the Minnesota DNR lists about 40 water bodies as infested with spiny waterflea.
How they spread
Spiny waterflea were first introduced to the Great Lakes through ballast water. Today, recreational boaters and anglers can inadvertently move them or their eggs on fishing line, bait buckets, live wells, or fishing nets.
Spiny waterflea research at MAISRC
- Tyler Ahrenstorff
- Bethany Bethke
- Valerie Brady
- Donn Branstrator
- Josh Dumke
- William French
- Gretchen Hansen
- Jodie Hirsch
- Katya Kovalenko
- Ryan Maki
- Heidi Rantala
Because it is not yet well understood how their establishment and proliferation translates into impacts on native game fish, MAISRC researchers are using paleolimnology data to more fully identify the long-term impacts of spiny waterflea. Researchers are also determining which commonly used gear is most likely to transport spiny waterflea, and evaluating the food web impacts of spiny waterflea on walleye.
- Sustaining walleye populations: assessing impacts of AIS
- Determining highest-risk vectors of spiny waterflea spread
- Characterizing long-term Spiny waterflea impacts using paleolimnology data
- New project launched to determine impacts of AIS on walleye (MAISRC newsletter)
- DNR launches high-tech study of food webs in Minnesota's largest walleye lakes (MAISRC in the news)
- Minnesota scientists dive deep to learn why walleye are stressed (MAISRC in the news)
- U of M's Donn Branstrator on spiny waterflea (MAISRC in the news)
- What sediment cores can tell us about Lake Mille Lacs, walleye, and spiny waterflea (MAISRC newsletter)
- Scientists Look to the Past to Figure Out the Walleye Collapse on Lake Mille Lacs (MAISRC in the news)
- Core samples from Mille Lacs Lake may explain walleye woes (MAISRC in the news)
- New MAISRC research to determine long-term impacts of spiny waterflea (MAISRC newsletter)