An Endangered Species in Ontario: The Slippery But Sensitive American Eel (Updated)

Post updated May 31, 2023

Toronto and Region Conservation Authority’s (TRCA) aquatic monitoring team have discovered 17 American Eels since 2020.

One was found in the invasive Sea Lamprey traps on the Humber River, and 16 were discovered during our annual boat electrofishing surveys. This brings the total number of American Eels found by TRCA’s monitoring team to 290 since 1989. (Yes, we have been collecting fisheries data on the Toronto waterfront for over 30 years!)

A member of TRCA's environmental monitoring team holds an American Eel, member of an endangered species

An Endangered Species:
Threats Faced by the American Eel

American Eels hatch as eggs in the Sargasso Sea near Bermuda, then float on ocean currents as larvae to coastal estuaries, where they reside as juveniles, before travelling upstream to freshwater rivers and lakes as adults. They face many threats on this long journey.

Hydro dams and other barriers, for example, often prevent their upstream migration, and the turbines used by hydroelectric generating stations on the St. Lawrence River also increase the risk of mortality. Habitat degradation and parasites also pose threats.

The American Eel was once commonly fished in Ontario, both commercially and recreationally. But declining numbers led to the discontinuation of this practice in 2004.

Good News!

Chart showing a recent increase in the number of American Eels observed on TRCA properties

We have seen a surge in numbers of eels found over the last few years: good news for the American Eel, which is currently listed as “Endangered” under the Ontario Endangered Species Act, 2007 and “Threatened” by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC).

This surge may be due to the transportation of millions of American Eels from the Maritimes to Ontario in the late 2000s, as well as the current stocking of young eels into the Upper St. Lawrence River and Lake Ontario.

The Ontario Ministry of Natural Resources and Forestry (OMNRF) and Ontario Power Generation have been the lead agencies involved in these activities, with support from the Fisheries and Oceans Canada (DFO).

TRCA’s Role

TRCA helps with the research by recording biological measurements and geographical coordinates of American Eels captured before releasing the species back into the water.

Our small role is a perfect example of how existing electrofishing surveys in Ontario can add value to our partners efforts. Since we are collecting fisheries data annually, we can also tracking the abundance of sensitive species, like the American Eel, or aquatic invasives, like the Rusty Crayfish or Round Goby, without spending thousands of dollars on specialized surveillance programs.

Did you know? Every American Eel we catch in Ontario is female; the males don’t make it up as far upstream into the Great Lakes Drainage Basin.

A member of TRCA's environmental monitoring team holds a recently discovered American Eel

Scientific data collection and research informs decisions affecting the natural areas and watercourses within our region. Connect with TRCA online.