title: Salinity effects on plasma ion levels, cortisol, and osmolality in Chinook salmon following lethal sampling.
abstract: 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 (Mg(2+)) and sodium (Na(+)) ions, cortisol and osmolality in fish exposed to saltwater challenges, and the ion and steroid hormone fluctuations over time following euthanasia in juvenile spring Chinook salmon (Oncorhynchus tshawytscha). Salinity of the euthanasia bath affected plasma Mg(2+) and Na(+) concentrations as well as osmolality, with higher concentrations in fish euthanized in saltwater. Time spent in the bath positively affected plasma Mg(2+) and osmolality, negatively affected cortisol, and had no effect on Na(+) concentrations. The difference of temporal trends in plasma Mg(2+) and Na(+) suggests that Mg(2+) may be more sensitive to physiological changes and responds more rapidly than Na(+). 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.
authors.affiliation: Department of Fisheries and Wildlife, Oregon State University, 104 Nash Hall, Corvallis, OR 97331-3803, USA. Electronic address: hadar.stewart@gmail.com.
authors.forename: Heather A
authors.initials: HA
authors.lastname: Stewart
authors.affiliation: Department of Fisheries and Wildlife, Oregon State University, 104 Nash Hall, Corvallis, OR 97331-3803, USA; Oregon Hatchery Research Center, 2418 East Fall Creek Road, Alsea, OR 97324, USA.
authors.forename: David L G
authors.initials: DL
authors.lastname: Noakes
authors.affiliation: Department of Fisheries and Wildlife, Oregon State University, 104 Nash Hall, Corvallis, OR 97331-3803, USA.
authors.forename: Karen M
authors.initials: KM
authors.lastname: Cogliati
authors.affiliation: Department of Fisheries and Wildlife, Oregon State University, 104 Nash Hall, Corvallis, OR 97331-3803, USA; U.S. Geological Survey, Oregon Cooperative Fish and Wildlife Research Unit, Department of Fisheries and Wildlife, Oregon State University, 104 Nash Hall, Corvallis, OR 97331-3803, USA.
authors.forename: James T
authors.initials: JT
authors.lastname: Peterson
authors.affiliation: Faculty of Biosciences and Aquaculture, University of Nordland, 8049 Bodø, Norway.
authors.forename: Martin H
authors.initials: MH
authors.lastname: Iversen
authors.affiliation: U.S. Geological Survey, Oregon Cooperative Fish and Wildlife Research Unit, Department of Fisheries and Wildlife, Oregon State University, 104 Nash Hall, Corvallis, OR 97331-3803, USA; Department of Fisheries and Wildlife, Oregon State University, 104 Nash Hall, Corvallis, OR 97331-3803, USA.
authors.forename: Carl B
authors.initials: CB
authors.lastname: Schreck
mesh_terms: D000818:Animals; D037901:Euthanasia, Animal; D005618:Fresh Water; D006854:Hydrocortisone / Q000097:blood*; D007477:Ions / Q000097:blood*; D009994:Osmolar Concentration; D054712:Salinity; D012474:Salmon / Q000097:blood* / Q000378:metabolism; D012623:Seawater; D012964:Sodium / Q000494:pharmacology; D014882:Water-Electrolyte Balance / Q000502:physiology
chemical_list: D007477:Ions; D012964:Sodium; D006854:Hydrocortisone
keywords: Cortisol; Delayed sampling; Euthanasia; MS-222; Magnesium; Oncorhynchus tshawytscha; Osmoregulation; Saltwater challenge; Smolt; Sodium