Structures to Prevent the Spread of Nuisance Fish from Lake Davis, California

Abstract

Abstract Methods to contain the spread of nuisance or otherwise undesirable fish species are relatively limited. I describe an unconventional method used to help restrict the movement of northern pike Esox lucius from a mountain reservoir into downstream waters. Reservoir managers designed, installed, and monitored steel structures (“graters”) that served to increase the likelihood that fish entrained in discharge from Lake Davis (Plumas County, California) would incur fatal trauma. Seven species of fish, cumulatively hundreds of individuals, were observed killed by the graters. Injuries induced included dismemberment, lacerations, abrasions, and contusions. No failures to induce fatal trauma to entrained fish were observed, though a few crayfish Pacifasticus spp. remained alive after only partial dismemberment. The graters were fabricated from commercially available steel and sized to fit over 10-in and 30-in discharge ports of the outlet works. Reservoir and fishery managers could adapt these designs fo...