Leon Bly Tunnel, which connects Eagle Lake to Willow Creek, was investigated to see if the water issuing from the tunnel was lake water or spring water and to check reports of its being inhabited by fish. We found that the water was similar to that of highly alkaline Eagle Lake, despite a block placed in the tunnel in 1986. Five species of fish were found in the tunnel, the same species inhabiting both Willow Creek and Eagle Lake, although the creek was much warmer and less alkaline than the lake. The fish originated from the creek. Fish in the tunnel were either not feeding or were consuming snails (Vorticifex sp.), the principal invertebrate present. The largest fish (35 cm SL) captured were rainbow trout (Oncorhynchus mykiss).
Moyle, Peter B.; Kennedy, Thomas; Kuda, Derek; and Martin, Laurie
"Fishes of Bly Tunnel, Lassen County, California,"
Great Basin Naturalist: Vol. 51
, Article 10.
Available at: https://scholarsarchive.byu.edu/gbn/vol51/iss3/10