Response of the catchable Largemouth Bass population to long-term water level reductions in Lake Perris, Riverside County, California

Most of the Largemouth Bass (LMB) fisheries in California are within reservoirs that fluctuate annually. These reservoirs can experience prolonged reductions to the water level if cultural demands exceed the supply of water that normal climatic conditions can replace. These extended periods of reduced capacity may impact the fisheries by eliminating critical littoral habitat and limiting carrying capacity within the affected reservoirs. Lake Perris, California experienced a prolonged mandatory drawdown due to a dam remediation project exacerbated by drought conditions that eliminated nearly half of the water volume in the reservoir for over a 14-year period. Annual mark-recapture population estimates of catchable LMB (>305 mm TL) were conducted to monitor the response of the bass population and compared with the water levels over the duration of the 14-year dam remediation project. The estimated number of catchable Largemouth Bass responded in nearly synchronous decline along with the water level over the duration of the altered hydrology.