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Loch, J. J. and S. A. Bonar (1999). Occurrence of grass carp in the Lower Columbia and Snake Rivers. Transactions of the American Fisheries Society. 128:374-379.

Forty-nine adult grass carp Ctenopharyngodon idella were observed migrating upriver past Lower Columbia and Snake river hydroelectric dams between August 1, 1996, and September 30, 1997, representing the first recorded sightings of this fish species in this system. From videotape records and visual counts, grass carp were estimated to range between 55 and 77 cm in total length (TL). One 7.7- kg, 86-cm individual captured in a gill net was identified as a sterile triploid. Although the source of these fish is unknown, their appearance in the Columbia and Snake rivers might have been related to extensive flooding that occurred in western Washington and Oregon in February 1996. The unintentional escape of grass carp into this large river system reemphasizes the need for the current requirement that all grass carp stocked in Pacific Northwest lakes be sterile triploids. It also suggests that increased attention to effective barrier construction and maintenance is important to prevent grass carp impacts in nontarget areas.