Reduction in the Longnose Sucker Population of Pyramid Lake, Alberta, in an Attempt to Improve Angling

An attempt was made to reduce the numbers of longnose or northern suckers and mountain whitefish in Pyramid Lake, Alberta, in the hope of improving the survival of introduced rainbow trout. The lake has an area of 320 acres and a maximum depth of 64 feet. Examination of its physical and biological characteristics show it to be oligotrophic and somewhat more productive than most of the other alpine lakes studied in the area. The results of a marking-and-recovery program suggested a population in the order of 27,000 fish of nettable size of which 75 percent were suckers, 22 percent mountain whitefish, and 3 percent game trout of three species. The removal of 27,600 longnose suckers in 7 years has eliminated the older age groups and has reduced the average weight of suckers caught from 5.5 to 1.6 ounces. However, the survival rate of young suckers, less than nettable size, increased. The removal of suckers has not been accompanied by any noticeable improvement in the survival of rainbow trout either during the 5 years of removal or in the 3 years which followed. The present game-fish harvest is less than that expected from a lake of this size. It is suggested that further fish-cultural efforts in this lake be concentrated on the lake trout.