Fig. 2. Plasma sodium (N>5) (A) and chloride (N>5) (B) levels in northern (black) and southern (grey) killifish before (pre) and after transfer from brackish water (BW; 10 g l^-1) to either brackish water (squares) or freshwater (FW; triangles). Data are expressed as means ± S.E.M. ^*Significant difference from time-matched brackish water control (P<0.05). Plasma Na data for northern killifish have been previously reported (Scott et al., 2004).