Fig. 3. Plasma glycerol levels in rainbow smelt Osmerus mordax. The date at which a controlled temperature decrease was initiated (i.e. 15 January 2004) is used as day 0. Water temperature (°C) is shown in parentheses. Values are means ± s.e.m., N=5 or 6 for all points. (A) Open circles, fish subjected to a controlled decrease in water temperature; filled squares, fish maintained at natural ambient temperature; filled triangles, fish maintained at elevated temperature. All fish were fed. (B) Fish subjected to a controlled decrease in water temperature without feeding.