Lake Cascade's Yellow Perch: On the Rebound?

By Dale Allen, Regional Fishery Manager Idaho Department of Fish and Game - Southwest Region For the last several years, Fish and Game fisheries staff has been working intensively to restore the yellow perch fishery in Valley County's Lake Cascade. The yellow perch fishery in the reservoir evaporated in 1997 and has yet to return. That crash dramatically changed angling use on the reservoir and resulted in the loss of millions of dollars annually to the local economy. The effort to restore the perch fishery continues; here's a status report on the process and the response documented in the reservoir's fish populations. The inability of yellow perch to rebound from critically low population levels has been the result of high mortality among newly produced yellow perch (baby perch, or young of the year perch; YOY for short). Most of that mortality was the result of predation by adult northern pikeminnow (formally called northern squawfish) which consumed nearly all the juvenile yellow perch produced each year. Once this problem was identified, Fish and Game staff developed a two-pronged strategy to expand the yellow perch population: increase the total number of yellow perch adult spawners and decrease adult northern pikeminnow populations. In come the perch On the perch side of the equation, Fish and Game has been busy during the past two springs capturing and stocking more than half a million wild yellow perch adults. In 2005 alone, 193,000 adult perch (better than 32,000 pounds of perch!) were caught and transplanted to Cascade. These fish were captured in several locations in Idaho, Oregon and Montana and transported to Lake Cascade in Department fish trucks. All indications are that the transplanted perch have survived well and that the 2004 transplants reproduced in the spring of 2005 (we expect both groups of transplants to reproduce in 2006 and beyond). Fisheries staff have observed and documented more YOY yellow perch this past summer than have been seen in many years, a very good sign. Survival of stocked adult perch also appears strong; catches of these fish in our sampling gillnets have increased by 15 times since just three years ago. Taken in total, these data have led to the decision to collect and transplant adult yellow perch into Lake Cascade for one more year, the spring of 2006. Out go the pikeminnow Even as this effort has been ongoing, Fish and Game fisheries staff has also been aggressively reducing the number of adult northern pikeminnow in the reservoir system. Fish toxicants have been utilized on major spawning runs of pikeminnow the past two springs. Also in 2002 and 2003, staff used weirs and traps in the rivers flowing into Cascade to capture and remove large numbers of pre-spawning pikeminnow. In the summers of 2004 and 2005, staff operated four to seven large floating stationary net traps in the reservoir itself to capture and remove additional adult northern pikeminnow. All these efforts seem to be having the desired effect; staff has documented steady declines in the number of adult northern pikeminnow counted in the spawning run and in sampling gillnets over the past two years. For example, the number of northern pikeminnow caught in sampling gillnets has dropped from nine per net to less than two per net from 2003 to 2005. These reduction efforts will continue in 2006. It appears that Lake Cascade's perch population may finally be gaining the advantage it needs to get back on its feet. Fish and Game staff has made good progress in removing the two main road blocks preventing the recovery of the Lake Cascade yellow perch fishery. The number of YOY perch produced has increased as a result of stocking additional adult yellow perch, and the survival rate of those YOY perch has also increased through reduced predation caused by the northern pikeminnow. The fisheries staff is hopeful that we can begin to consistently produce YOY perch and have them survive to adulthood. In doing so, we just might create a self-sustaining yellow perch fishery in the near future.