Rehabilitation of a Lake Superior Steelhead Population by Stocking Yearling Smolts

摘要

The steelhead Oncorhynchus mykiss population in the upper Chocolay River was successfully rehabilitated in the 1980s after being below carrying capacity for around 30 years. Rehabilitation was accomplished by stocking large (175-184 mm), yearling Michigan-strain steelhead smolts in 1983, 1984, and 1985 at an upstream location with good spawning substrate. Most adult steelhead sampled in the 1986-88 spawning runs were hatchery fish, and all of these were the Michigan strain stocked in 1983-85. The composition of steelhead spawning runs in the upper Chocolay River changed from mostly hatchery to all wild during 1986-92. Steelhead spawning activity stabilized at about 0.9 adults and 0.6-0.8 redds per 100 m of stream. Juvenile steelhead abundance in the upper Chocolay River increased in 1985 and 1986, then leveled off between 1986 and 1992 at what appeared to be carrying capacity. No further steelhead stocking should be done in the upper Chocolay River unless juvenile populations decrease substantially, and future stocking of hatchery fish should only be done in streams with steelhead populations below carrying capacity.