Fig. 2. Changes in plasma Na⁺, Cl^–, K⁺ (A–C) and cortisol (D–F) concentrations and gill Na⁺/K⁺-ATPase activity (G–I) in lake trout (A,D,G), brook trout (B,E,H) and Atlantic salmon (C,F,I) following gradual transfer from 0 p.p.t. to 10, 20 and 30 p.p.t. Salinities: before day 0, 0 p.p.t.; day 0–7, 10 p.p.t.; day 7–14, 20 p.p.t.; day 14–35, 30 p.p.t. Symbols in A–C: circles, Na⁺; triangles, Cl^–; squares, K⁺. Each value represents the mean ± s.e.m., N=8. Groups with different lowercase letters are significantly different (P<0.05, Tukey–Kramer test).