Smolting Success of Hatchery‐Raised Steelhead Planted in a Michigan Tributary of Lake Michigan

Four groups of hatchery‐raised steelhead Salmo gairdneri were marked and released in the Little Manistee River, a Michigan tributary of Lake Michigan. The groups were yearlings, fall fingerlings, fall yearlings, and large yearlings. Percent smoolting, cost per smolt, timing of smolting, and an index of residual river populations were examined for each group. Smolting was monitored with traps installed near the mouth of the river. Estimates of residual river populations were obtained by electrofishing. Percent smolting was very low (0.5‐7.1%) for the yearlings, fall fingerlings, and fall yearlings, but much higher for the large yearlings (48.2%). Percent smolting was inversely related to the length of time each group spent in the river. The cost of producing one smolt was lowest for fall fingerlings and large yearlings at $0.69 and $1.11, respectively. Both hatchery‐raised and wild steelhead smolted during May and early June, and peak migrations occurred in mid‐May. Fairly high standing crops of the yearling and fall fingerling groups were found at the planting site during the first fall following planting (age‐1 + fish). Those hatchery‐raised fish that remained in the river were found within 1.75 miles of the planting site. The large yearlings were, by far, the most economical and practical group considered, in terms of both cost and numbers needed to meet specific management goals.