What is the impact? 
Compared to other zooplankton species, it can eat up to three times more food, competing directly with native zooplankton and fish, and reducing both the amount and kinds of prey available.
Also, although some native fish species feed on spiny water flea as an alternative food source, smaller fish (under 10 cm long) that attempt to eat these fleas cough them up because of their long tail spine. The resulting lack of food or prey for small fish may affect their growth and survival, and contribute to a decline in their numbers.
Adding spiny water flea to the food web in Ontario lakes may also affect biomagnification of contaminants such as mercury (Hg). Currently, research is emerging on the impact of this species to contaminant burdens, which may build through the food web, affecting top predatory fish like lake trout.
Spiny water flea can affect fishing activity as well, becoming entangled in fishing lines and downrigger cables. The animals look like straight pins along the downrigger or line, and may sometimes raise and lower their tails.
More information: Spiny Water Flea on Invading Species Web Site.
