Lake Cascade Yellow Perch Restoration Update

By Dale Allen, Regional Fishery Manager Idaho Department of Fish and Game - Southwest Region Lake Cascade now contains many more perch and fewer pikeminnow than it did a year ago. Earlier this year, Fish and Game announced a two-pronged approach to restore yellow perch fishing in Lake Cascade. The first involved an effort to increase the numbers of adult yellow perch spawners. The second prong involved reducing the lake's predatory northern pikeminnow population. In April 2004, Fish and Game staff moved more than 100,000 adult yellow perch into Lake Cascade. Unfortunately, most had either spawned previously or dropped their eggs because of the capture, handling or transport stress incurred on their trip to Lake Cascade. While this loss of perch eggs was unfortunate (though not unexpected), we documented good survival of the transplanted yellow perch. The bottom line was that perch spawning activity in 2004 was limited primarily to perch already residing in the lake. From May to mid-June 2004, the department used an electric barrier in the North Fork of the Payette River just above Lake Cascade to stop the spawning migration of suckers and northern pikeminnow. Stymied by the electric current in the river, the fish piled up behind the weir. Biologists then treated the river with a precisely calculated dose of rotenone, a registered fish toxicant, to kill these fish. Chemical treatments were conducted four times; treatments ended when the northern pikeminnow spawning migration ceased. An estimated 11,000 northern pikeminnow spawners were killed during these efforts. Also beginning in May 2004, the department began placing large floating fish traps in the upper end of Lake Cascade to capture northern pikeminnow. Operated into September, the traps were emptied several times per week. Between the seven traps, technicians captured and killed about 2,200 adult northern pikeminnow, releasing all other species alive. Fisheries biologists estimate that these two efforts cut Lake Cascade's northern pikeminnow population in half. Thanks to the natural perch spawning and the pikeminnow reduction efforts, a larger number of young yellow perch in the reservoir were documented this fall than have been seen in many years. This bodes well for a strong year class of yellow perch to be produced and survive in 2005. The hope is that this 2005 production of yellow perch will serve as the foundation for a return to Lake Cascade yellow perch fishing in about four years.