Alder Lake is managed primarily for lake trout, with walleye a secondary species. Both species have been self-sustained in this lake for decades. Smallmouth bass and northern pike are also present, but their numbers have typically been low. That said, smallmouth bass are not sampled well in gill nets, and angler reports suggest they are more abundant in this lake than the gill net catch would indicate.
As has usually been the case in this lake, modest numbers of lake trout were found in 2015, with a few larger fish present. The 2015 catch was similar to catches observed in previous surveys of this lake done since 1969. Five lake trout year classes were included in the catch, and although none had been strong, they indicated natural reproduction had been successful on a fairly regular basis. It appeared that growth, at least of young lake trout, had been about average for the area.
Fair numbers of walleye were found in 2015, although none longer than 24 inches were taken. The 2015 gill net catch was similar to catches observed in other surveys of this lake since 1992, but was lower than most catches seen in the lake prior to that year. That difference may be in part due to differences in survey timing. Earlier surveys were done in August, when walleye gill net catches tend to be higher compared to catches in June surveys. Six year classes, all naturally produced, contributed to the 2015 walleye catch, with the strongest apparently produced in 2012. Growth of young walleye had been average or better for this area, despite the lack of a good yellow perch forage base. Walleye taken in this survey were fat, and in very good condition. Some of the walleye collected in deeper waters had been feeding on sculpins.
Gill net catches of other species were low. No yellow perch were taken, but the species has been collected in low numbers in most past surveys of this lake. Two northern pike and two smallmouth bass were also caught. Anglers interviewed during the survey reported good fishing for smallmouth bass. Alder Lake provides cool-water refuge areas needed by larger northern pike, but lacks high-quality cold-water forage species like cisco or whitefish.