Just Passing Through

Archival records and technical reports have noted 59 fish species, from 21 families, found in the Rideau River and Canal during the last century. Although the Rideau River Biodiversity Project found almost half that number, the results do not suggest that the other half have disappeared from the Rideau River.

A considerable number of the 59 fish species found during the last century were not native, local residents, but were simply passing through. Some arrived via Rideau River tributaries, the Ottawa River or the St. Lawrence River. Also, attempts had been made to introduce various trout species to the Rideau River; the species did not survive because the River's water is too warm. Most of the "missing" species never really belonged in the River.

Eastern silvery minnow, Hybognathus regius.

The loss of this species may be an early warning that physical disturbances such as habitat loss and increased turbidity are harming the fish populations of the Rideau River. Water level fluctuations may have caused additional stress to the eastern silvery minnow.

	A Piranha?! In the Rideau? A fish that resembled a pacu or a piranha (like this one) was found in the Rideau River in 1994. Believe it! A fish that was either a piranha or a pacu was found, dead, in the shallows at Dows Lake in Ottawa, in October 1994. The South American species could not be identified with certainty, but the animal was 30 to 35 cm long! [18] In June and August 1999, oscars were caught in the Rideau Canal in downtown Ottawa. The two exotic fish measured 20 to 25 cm long. The species originates in South America. [19] The individuals of these exotic species are unlikely to survive the winter or to reproduce in the Rideau River. The impact these aggressive predators will have on native fish is unknown. Piranhas and pacus are now established in 33 of the United States, thanks to pet owners who released exotic aquarium animals into different waterways. Considerable damage to native fish has resulted. [20]