Is Reclamation's Razorback Sucker Augmentation Program in Lake Havasu successful?
Goals of this project are to:
* Determine the population size of razorback suckers living in the Colorado Rivers between Davis and Parker Dams
* Determine razorback distribution and habitat use in the study area
* Determine survival rates of repatriated suckers based on different agencies stocking approaches
Reclamation is currently operating under a jeopardy opinion from the U.S. Fish and Wildlife Service (USFWS) which requires razorback sucker population augmentation and population monitoring to determine success of these efforts in order for Reclamation to continue normal water deliveries.
Need and Benefit
State and Federal agencies have been augmenting the endangered razorback sucker population in Lake Havasu and the Colorado River upstream to Davis Dam since the early 1990s. A total of approximately 30,000 fish have been stocked in this reach of the Colorado River. Previous sampling efforts have shown that some fish have survived. These efforts have contacted about 250 of these fish. The majority of these fish were captured in the Park Moabi, Pulpit Rock, and Blankenship Bend areas of this reach of river. Not enough marked fish were captured during previous sampling efforts to accurately measure survival rates of repatriated fish.
Razorback suckers appear to be widely distributed throughout the upper reservoir and river, making their capture difficult. Previous attempts to capture fish have centered on the spawning season when razorback suckers congregate. However, the majority of female repatriated suckers were not old enough to be sexually mature and participate in spawning. Today, the majority of the surviving repatriated suckers are 6 to 8 years old. We anticipate that both sexes will actively spawn in the future. If spawning areas can be found, those concentrations of fish will be vulnerable to capture with nets. This should increase our chances of marking and recapturing larger numbers of fish. We propose to focus our sampling effort on the spawning season. We also will use radio transmitters on sexually active males to help locate spawning areas. Past studies have shown that males normally remain at the spawning site while females are more prone to wander between spawning sites. If we find spawning groups, we will be able to accurately estimate the survival rates of repatriated suckers. Field surveys and data analysis will be closely coordinated with Dr. Paul Marsh (Arizona State University [ASU]) who is conducting similar work downstream of Parker Dam.
Bureau of Reclamation Review
The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.
The Status of Razorback Suckers between Davis and Parker Dams (Lake Havasu), 2003-2005 (interim, PDF,
By Rick Wydoski
Report completed on May 06, 2014