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Asian Swamp Eel (Monopterus albus)
Photo credit: Biodiversity Heritage Library,


(Leuciscus idus)

Report this Species!

If you believe you have found this species anywhere in Pennsylvania, please report your findings to iMapInvasives by submitting an observation record.

Species at a Glance

The ide, also called the orfe, is a large-bodied freshwater fish and member of the minnow family. It is valued as a sport fish in many countries and has been introduced to a number of locations for this purpose. Concerns have been raised over its potential to damage native aquatic ecosystems, but more research is needed to determine actual impacts.


This chunky fish has a distinct arch in the back and belly. The head is small and bluntly pointed and the tail has a fork in it. Two color forms exist, including the wild form and ornamental form. The wild form is a grayish-olive color on the back and upper sides, paling to silver on the sides and a silvery-white on the belly. Both anal and pelvic fins are reddish in color. The ornamental variety has a bright orange back, silver-orange sides and belly, and a bright orange tail and dorsal fin. These two color morphs are known as silver and golden ides respectively. Golden populations may revert to wild coloration over time.

Similar Species

This species may be confused with the European rudd (Scardinius erythrophthalmus); however the pectoral, pelvic, and anal fins of the rudd are a distinctive bright reddish-orange color. In addition, the iris of the rudd’s eye is yellow to orange, often with a red spot that can cover the pupil, which is absent in the ide.


The ide prefers to inhabit clear, clean pools of medium-to-large rivers, ponds, and lakes. It retreats into deep holes over winter. The ide can also tolerate higher levels of salinity, giving it the ability to colonize brackish water and estuarine habitats.


Valued as an ornamental pond fish, the ide has been intentionally introduced to new locations for ornamental purposes and angling. Intentional releases and escape by flooding have also allowed this species to move to new locations.


Native to Europe, the ide was first imported in 1877 by the U.S. Fish Commission. In 1889, an estimated 20 ide escaped into the Potomac River from fish ponds in Washington, D.C. during a flood event. The ide is established in the Mid-Atlantic in the lower Potomac River in Maryland, and it has also been collected in Virginia and West Virginia. Failed populations have also occurred in New Jersey, New York, North Carolina, and Pennsylvania.


Note: Distribution data for this species may have changed since the publication of the Mid-Atlantic Field Guide to Aquatic Invasive Species (2016), the source of information for this description.

Environmental Impacts

Like other members of the minnow family, the ide is a prolific breeder and large females may contain tens of thousands of eggs. While little is known about the impact of this species, many researchers believe the ide has the potential to become more of a problem to aquatic ecosystems than either goldfish or common carp.


Information for this species profile comes from the Mid-Atlantic Field Guide to Aquatic Invasive Species (2016).

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