This report summarizes progress for the first year of a three year Habitat Conservation Fund project aimed at enhancing rainbow trout populations in alkaline lakes. Broodfish were collected from highly alkaline Green and Stump lakes in mid-May 1991 and survival of their progeny in alkaline study lakes are to be compared in 1992.
An in-stream acclimation study was conducted on May 30, 1991 at 83 Mile Creek, a small inlet to Green Lake affording an alkalinity gradient in-stream to mid-gradient to in-lake proper. One-year-old hatchery-reared rainbow trout that were acclimatized over seven hours in the pH gradient before being held in-lake proper for a 24 hour period had a mortality rate of 1% compared to 9.3% for fish placed directly into alkaline lake water.
Samples collected by gillnets from three rainbow trout strains stocked into Lake 5567 suggest that after a prolonged period (102 days) in an alkaline lake, mortalities may occur differentially between strains. The Bootjack strain was recovered in significantly greater numbers over the Tzenzaicut and Pennask strains at a ratio of 1.7:1:1. Strain-specific tolerance to high alkaline water conditions and further acclimation comparisons between strains are to be investigated.
Yesaki, Tim Y., Tsumura, Kanji. 1992. Alkaline Lakes Enhancement: Habitat Conservation Fund Progress Report (1991-92). Ministry of Environment, Lands and Parks. Fisheries Project Report. RD31