Efficacy of Shoal Liming for Rehabilitation of Lake Trout Populations in Acid-Stressed Lakes

Abstract

We tested the efficacy of adding crushed limestone of various grades (particle sizes) to spawning shoals to increase survival of eggs and embryos of lake trout Salvelinus namaycush in acidic lakes. Spawning lake trout did not avoid shoals where limestone was applied, and egg density from natural spawning was the same in both treated and untreated areas. Experimental limestone treatment increased pH and calcium while decreasing concentrations of inorganic aluminum in the interstitial water of the spawning shoals. Under ambient conditions in which control embryo mortality was high, incubation within limestone substrate significantly increased the survival of embryos. We find that shoal liming is an effective management technique to improve lake trout embryo survival in acidic lakes where whole-lake water quality can still support juvenile and adult lake trout.