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Razorback Suckers Found in Lake Powell


photo: Waterfall on San Juan River where it empties into Lake Powell
Waterfall on San Juan River where it empties into
Lake Powell

Razorback suckers, an endangered fish found in the Colorado River Basin and one of the four focal species for the Upper Colorado and San Juan Basin Recovery Implementation programs, were recently found in Lake Powell where the San Juan River enters the reservoir. Biologists with the San Juan Recovery Implementation Program had long suspected that these fish might be using this area, but the remoteness of the area, combined with the inaccessibility to the lower river due to a large waterfall, prevented effective surveys from being conducted. In 2011 the SJRIP made a concerted effort to find some of these fish and developed a project to set nets and conduct electrofishing in Lake Powell where the San Juan River ends  The project was funded using Upper Colorado River Basin Fund power revenues provided by Reclamation and was jointly conducted by the U.S. Fish and Wildlife Service (Grand Junction Office), Utah Department of Wildlife Resources (Moab Field Station), and the Navajo Nation who own the lands on the southern boundary of the river and reservoir.

To get to the study area requires an 85 mile boat ride from Bullfrog Marina on Lake Powell, the closest access point to the area. The field crews boat 35 miles down Lake Powell from Bullfrog and turn east into the San Juan River arm and proceed another 50 miles to where the reservoir and river meet. Once in the study area the crews erect large tents to escape the high winds, blowing sand, rain, sleet, snow, and blazing sun that typify this area from March through July.  The biologists spend 10 days on each trip setting nets and electrofishing to capture these elusive fish. Once captured the fish are weighed, measured, and scanned for a PIT (Passive Integrated Transponder) tag that is inserted in fish when they are released from a hatchery or captured in the river upstream. Some fish have a sonic tracking device inserted in their abdominal cavity which allows the biologists to track the fish and set nets near where they go in the hopes of catching additional fish. The use of these ‘Judas’ fish has worked very well in Lake Mead to locate spawning aggregations of razorback suckers in the lake and it seems to be working to help locate fish in Lake Powell as well.

While the project has not been completed this year, the results to date are very promising.  Well over 50 fish have been captured, with many of the fish not possessing the PIT tags that would indicate that the fish came from a hatchery. This could suggest that the fish are wild-spawned fish that recruited to an adult size, which has been a rare to nonexistent event in the river systems throughout the Colorado Basin.  Additionally the size and weight of the fish indicate that they are extremely healthy, in fact they represent the largest specimens of the fish ever captured in the San Juan River system!  Several of the fish captured were in spawning condition and the biologists are continuing to look for larvae, which would suggest that they are successful at spawning in the reservoir.

The project will be continued in 2012 with the hope that even more fish will be found and specific habitat can be identified where the fish can be captured. A similar project is ongoing in Lake Mead in the area where the Colorado River flows in from lower Grand Canyon. That project is a joint project conducted by Reclamation’s Lower and Upper Colorado regions and has identified the only known population of razorback suckers in the Colorado River Basin with a recruiting population.


photo: Biologists with largest razorback sucker ever captured in San Juan River system
Biologists with largest razorback sucker ever captured in the
San Juan River system
photo: Typical habitat in Lake Powell where razorback suckers have been captured
Typical habitat in Lake Powell where razorback suckers
have been captured

 

Last updated: June 29, 2011