Spiny Waterflea and Fishhook Waterflea

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• Aquatic invaders
• Pathways of invasion
• Threats to the environment, the economy and society
• Focus on an invader
• What you can do

• What to do if you find aquatic invasive species?

Spiny Waterflea

(Bythotrephes longimanus)

Fishhook Waterflea

(Cercopagis pengoi)

Spiny Waterflea and Fishhook Waterflea are 2 tiny crustaceans, part of zooplankton, which live suspended in water and drifting with currents.

Characteristics

  

Origin

Spiny Waterflea and Fishhook Waterflea are native to the region of the North Sea and to central Europe and Asia. They were introduced to North America due to ballast waters from ocean-going vessels. The two species were found for the first time in Lake Ontario, Spiny Waterflea in 1982 and Fishhook Waterflea in 1998. Both species can be found in the interior waters of Northeast America, in particular the Great Lakes, the St. Lawrence River, Lake Champlain and, since 2019, in the Richelieu River. Spiny Waterflea is also found in Lake Témiscamingue since 2018 and has been reported in the Lake McConnell area of the Ottawa River in 2021.

Habitat

Spiny Waterflea lives in all types of aquatic habitats (fresh and salt waters). Although it prefers large and deep lakes with temperate and well-oxygenated waters, it can also be found in less oxygenated waters rich in organic matter. On the other hand, Fishhook Waterflea prefers fresh waters with low salinity, but tolerates a wide range of temperatures, salinities and depths. It can migrate towards deeper waters during the day and swim closer to the surface at night. Usually it is found in pelagic zones far from the coast, but in the Richelieu River it is found closer to shore.

Similar species

Spiny Waterflea and Fishhook Waterflea look similar to some native Waterflea species, such as Daphnia. However, the drop shape body of the Daphnia only measures up to 0.5 cm and its tail is very short, accounting for only a quarter of the total length.

Daphnia longispina

Spiny Waterflea (bottom) and Fishhook Waterflea (top)