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Spiny Waterflea

Spiny Waterflea

Spiny waterfleas (Bythotrephes longimanus) are typically found in areas of deep, cold, open water. In Vermont, spiny waterfleas are currently found in Lake Champlain.


Spiny waterfleas are crustaceans about ½-inch long. They have a long, spiny tail that makes up about 70 percent of their body length. The tail has one to four pairs of barbs. Spiny waterfleas have large black eyes and four pairs of legs. Individual spiny waterfleas are difficult to see but they often collect in masses on fishing line, downrigger cables, anchor ropes, and other tackle. These masses appear as jelly-like clumps with tiny black spots.   


Spiny waterfleas reproduce rapidly, quickly forming large populations. They feed on microscopic species of native plants and animals, also known as phytoplankton and zooplankton, and can reduce their abundance. By reducing native zooplankton abundance, spiny waterfleas impact fish populations whose young also rely on zooplankton as a food source. Native fish species also have difficulty eating spiny waterflea because of their long tail spines. Additionally, spiny waterflea masses can interfere with fishing and cause damage to gear.

Control and Prevention

There are no control methods for spiny waterflea infestations. Preventing their spread to new waters is the best management option. 

Spiny waterfleas are usually spread unintentionally on boating and fishing equipment. They collect on fishing line, downrigger cables, boat anchors, and other equipment and can be transported in livewells, bait buckets, or other wet areas of boats and vessels. Eggs can also resist drying and freezing conditions, increasing their chances of survival and likelihood of being spread and establishing new populations.

Practicing Clean, Drain, Dry spread prevention methods when boating and recreating on the water is very important. Drain all water from your boat, canoe, kayak, and other vessels and any equipment used in the water. Clean off any mud and plant fragments and dispose of properly. Dry all damp areas of boats and vessels, such as livewells and bilges, with a towel and let air dry in the sun for at least five days before using in another waterbody. If this is not possible, rinse equipment with hot, high-pressure water.

Learn More

VT Invasives

For more on spread prevention

VT Department of Environmental Conservation

For volunteer opportunities to help monitor and protect Vermont's waters


VT Invasives

Lake Champlain Basin Program 

Minnesota Department of Natural Resources

US Geological Survey Nonindigenous Aquatic Species