title: Renal, respiratory and ionic regulation in Atlantic salmon (Salmo salar L.) kelts following transfer from fresh water to seawater.
abstract: Atlantic salmon may return to the sea after spawning in fresh water. These fish, known as kelts, reportedly show a limited ability to hypoosmoregulate. However, this study shows that fresh-water-adapted kelts exposed to seawater demonstrate rapid adaptation (within 48 h) in osmoregulatory parameters to values characteristics of seawater-adapted salmonids. The urine flow rate falls from 1.2 to 0.2 ml.kg-1.h-1 within 24 h. Over the same period, urine osmolality increases from 48 mosmol.kg-1 to become isosmotic with the plasma, and Mg2+ secretion by the kidney tubules elevates the urine concentration from 0.5 to 100 mmol.l-1. As is characteristic for marine teleosts, kelts drink seawater and process the ingested water in the gut to replace body water lost by osmosis to the hyperosmotic medium. Seawater exposure causes a marked hypoxia, arterial oxygen tension falling by 43% within minutes and persisting for at least 4 days at this low level. This is associated with large changes in blood pH and acid-base balance. The physiological mechanisms involved in adaptation to a hyperosmotic external medium are discussed, and the osmoregulatory capacity of kelts is compared with that of salmon at other stages of the life cycle.
authors.affiliation: Freshwater Fisheries Laboratory, Pitlochry, Perthshire, UK.
authors.forename: C
authors.initials: C
authors.lastname: Talbot
authors.forename: R M
authors.initials: RM
authors.lastname: Stagg
authors.forename: F B
authors.initials: FB
authors.lastname: Eddy
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D002320:Cardiovascular Physiological Phenomena; D004068:Digestive System Physiological Phenomena; D005618:Fresh Water; D007668:Kidney / Q000502:physiology; D012143:Respiratory Physiological Phenomena; D012474:Salmon / Q000254:growth & development / Q000502:physiology*; D012623:Seawater; D014882:Water-Electrolyte Balance / Q000502:physiology*