Effect of Spiny Water Flea on Lake George

extreme closeup of spiny water fleaThe spiny water flea (Bythotrephes longimanus) is an aquatic invasive zooplankton native to Northern Europe and Asia. It was first discovered in Lake George in 2012.

It is not an insect as its name might sound, but is actually a cladoceran, which is a type of crustacean.

While it is no danger to humans or domestic animals, spiny water fleas can have a huge impact on aquatic life in lakes and ponds due to their rapid reproduction rates.

There are no known current management options for infestations other than spread prevention.

sample bottle showing tiny water fleas
Spiny water flea collected by LGA staff in Lake George in the north basin just West of Mallory Island on July 31, 2012

The Threat

Spiny water fleas produce rapidly through parthenogenesis, commonly known as asexual reproduction, which means that no males are required and populations can explode in number.

During the summer when the water is warm, spiny water fleas reproduce rapidly, with each spiny water flea able to produce up to 10 new ones in just two weeks. This rapid reproduction rate can have a huge impact on aquatic life and recreational activities in lakes and ponds for several reasons:

  • Direct Competition — Spiny water fleas are voracious predators of small zooplankton, like Daphnia, an important food for young native fishes and other native aquatic organisms. Zooplankton is also an important food source for forage fish that are, in turn, eaten by larger sport and commercial fish. In this manner, zooplankton community shifts can have an effect through the food chain. And because of their ability to reproduce quickly, this feature enables them to monopolize the food supply.
  • Ecological Disadvantages — Although the spiny water flea can fall prey to fish, their spine seems to frustrate most small fish, which tend to experience great difficulty swallowing the animal. Spiny water fleas adversely affect the growth rates and survival of young fish, due to the competition for food.
  • Nuisance Buildup — Spiny water fleas collect in masses on fishing lines and downrigger cables. These masses can clog the first eyelet of rods, damage a reel’s drag system, and prevent fish from being landed.

Identifying the Spiny Water Flea

closeup of spiny water flea showing barbs
What looks like bristly globs of jelly with black spots is actually many spiny water fleas tangled on a fishing line.

See our Spiny Water Flea Information Sheet. Spiny water fleas are difficult to distinguish without magnification, usually 1/4 – 1/2 inches (5-13 mm) in total length.

They have a long barbed tail filament which makes up 70% of their total body length. The tail can have 1-4 pairs of barbs running down it. Because they are so small, individual water fleas often go unnoticed. However, masses of water fleas are easily visible on fishing gear and other equipment.

Known Spiny Water Flea Locations and Habitat

The spiny water flea was first found in North America in 1984 in Lake Huron. Thought to have arrived in ballast water, it rapidly spread throughout the Great Lakes. It was confirmed in Lake Ontario and Lake Erie in 1985, Lake Michigan in 1986 and Lake Superior in 1987.

Spiny water flea had not been confirmed in eastern New York until 2008 when it was found in Great Sacandaga Reservoir, whose outlet is just about 20 miles west of Lake George. It was then found in Peck Lake in 2009, Stewarts Bridge Reservoir in 2010 and Sacandaga Lake in 2010. In July 2012, spiny water flea was confirmed in the Glens Falls Feeder Canal and the Lake Champlain Canal — just weeks before being found in Lake George. In July 2014 spiny water flea was found in Piseco Lake and Lake Pleasant.

Spiny water flea follows its prey (plankton), staying in deeper waters during the day and coming up closer to the surface at night to feed in a daily vertical migration throughout the water column. First found off Mallory Island on the east side in the north basin of the lake, it most likely can be found around 10-20 meters deep in Lake George in the main part of the northern basin of the lake.

Scientific literature shows that spiny water flea is limited to regions where water temperature ranges between 4 and 30°C and salinity values between 0.04 and 8.0%, but it prefers a temperature between 10 and 24°C and salinity between 0.04 and 0.4% (Grigorovich et al. 1998).

Lake George’s salinity is around 1.8% and water temperature ranges from about 4°C to 30°C, so, unfortunately, it appears this invader will do just fine here in Lake George.

Prevent Spread by Boating Clean, Drained and Dry

Currently, there are no successful means to control or eradicate this and many other aquatic invasive species, so preventing their spread is the only means for reducing their impacts on native aquatic communities. Fishing and boating equipment is the most likely means of spread, so boat clean, drained and dry.

Additional Information

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