David L. G. Noakes Karen M. Cogliati James T. Peterson Martin H. Iversen Carl B. Schreck Heather Stewart 2016 <p><span>Studies on hydromineral balance in fishes frequently employ measurements of electrolytes following euthanasia. We tested the effects of fresh- or salt-water euthanasia baths of tricaine mesylate (MS-222) on plasma magnesium&nbsp;(Mg</span>²⁺<span>) and sodium (Na</span>⁺<span>) ions,<span> cortisoland osmolality in fish exposed to saltwater challenges, and the ion and steroid</span><span><span>&nbsp;</span>hormone fluctuations over time following euthanasia in juvenile spring Chinook salmon (</span></span><i>Oncorhynchus tshawytscha</i><span>). Salinity of the euthanasia bath affected plasma Mg</span>²⁺<span><span>&nbsp;</span>and Na</span>⁺<span>concentrations as well as osmolality, with higher concentrations in fish euthanized in saltwater. Time spent in the bath positively affected plasma Mg</span>²⁺<span><span>&nbsp;</span>and osmolality, negatively affected cortisol, and had no effect on Na</span>⁺<span><span>&nbsp;</span>concentrations. The difference of temporal trends in plasma Mg</span>²⁺<span><span>&nbsp;</span>and Na</span>⁺<span><span>&nbsp;</span>suggests that Mg</span>²⁺<span><span>&nbsp;</span>may be more sensitive to physiological changes and responds more rapidly than Na</span>⁺<span>. When electrolytes and cortisol are measured as endpoints after euthanasia, care needs to be taken relative to time after death and the salinity of the euthanasia bath.</span></p> application/pdf 10.1016/j.cbpa.2015.11.011 en Elsevier Salinity effects on plasma ion levels, cortisol, and osmolality in Chinook salmon following lethal sampling article