Razorback Sucker in Lake Mohave

The Razorback Sucker (Xyrauchen texanus) is one of four large bodied river fish species native to the Colorado River Basin. Currently listed as endangered under the authority of the Endangered Species Act of 1973 (USFWS 1991), the Razorback Sucker was historically abundant throughout the Basin and was predominantly found in the main stem river and major tributaries of Arizona, California, Nevada, New Mexico, Utah, and Wyoming (USFWS 1998). The current distribution and abundance of Razorback Suckers are greatly reduced from historic levels, mainly due to main stem dam construction and the introduction of non- native game fish species (Minckley et al. 1991). Populations have persisted following the creation of reservoirs in the lower Colorado River Basin, but this has only been possible due to recruitment events occurring soon after dam closures (Minckley 1983) and ongoing fish augmentation (Mueller 2006).

Current monitoring efforts focus on identifying annual spawning sites, locating and capturing adult razorback sucker, recording biological data of captured fish, collecting tissue samples from captured fish for genetic analyses, and using capture data and remote scanning of passive integrated transponder (PIT) tags to provide zone specific and lake-wide population estimates. The adult population in Lake Mohave remains the most genetically diverse among Razorback Sucker populations and acts as the primary brood stock for this species. The Lower Colorado River Multi-Species Conservation Program (LCR MSCP) currently captures the offspring of this stock directly from Lake Mohave and rears them at Willow Beach National Fish Hatchery for future repatriation.

Monitoring the Lake Mohave Razorback Sucker population through annual sampling and collection efforts will ensure the availability of suitable offspring for future LCR MSCP augmentation needs. This monitoring effort will also support ongoing Razorback Sucker conservation efforts by providing sound data on which management decisions can be made.