Swimming performance of flannelmouth sucker

in relation to proposed Glen Canyon Dam modifications


The flannelmouth sucker, Catosomus latipinnis, is one of the few native fish that remain in the Colorado River below Glen Canyon Dam. Recent studies by Weiss, 1993 and Theime, 1997 have indicated low survival and recruitment of juveniles into the adult population, which may indicate population declines. Adult flannelmouth suckers travel up the Paria river, a tributary of the Colorado, to spawn. The juvenile fish live in the Paria until high flows caused by late summer monsoons flush them out into the Colorado River. The cold, (ten degrees Celcius) swift flows of the Colorado caused by water released from Glen Canyon Dam, are believed to impair swimming ability of juvenile flannelmouth suckers, leading to direct mortality and increased predation. In an effort to stop the decline of native fish in the Grand Canyon area, the Bureau of Reclamation has proposed installing a multi-level intake structure on Glen Canyon Dam. This would allow warm water from the surface of the reservoir to be mixed with hypolimnetic, cold water in order to raise the water temperature downstream by as much as four degrees Celsius.

In Cooperation with the US Fish and Wildlife Service, flannelmouth suckers are being reared from eggs at The University of Arizona Environmental Research Laboratory in Tucson. Fatigue velocity tests on young-of-the-year fish will be conducted in a plexiglass swim tunnel in order to test the effects of fish size, temperature and flow on the ability to maintain position in a current. Fish 20 to 80 mm in length will be subjected to incremental flow velocities within the range of their swimming ability. Tests will be conducted at ten degrees Celsius, which represents the current temperature of the Colorado River, 14 Degrees Celsius, which is the temperature that could be achieved if modified intake structures are placed on Glen Canyon Dam and 20 degrees Celsius which represents pre-dam temperatures. The size and temperature at which young-of-the-year flannelmouth suckers are physiologically able to survive in the Colorado River below Glen Canyon Dam will be determined. This information will be important in deciding upon appropriate management actions for the flannelmouth sucker.

For questions or comments on this project contact:

David Ward

The University of Arizona

Room 104 Biosciences East

Tucson, AZ 85721

e-mail: dward@ag.arizona.edu

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