Osmoregulation in Salmon and Sea Trout Alevins

Abstract

Changes in survival, body-water content, body electrolyte concentration and Na+ turnover rates were studied in alevins of Atlantic salmon (Salmo salar L.) and sea trout (Salmo trutta L.) at different developmental stages following exposure to various dilutions of sea water. In 100% sea water, salmon alevins at 9 days post-hatch survived approximately 6 h, and sea trout alevins 13 days post-hatch survived approximately 4 h. In both species, survival in hyperosmotic media decreased and rates of dehydration and Na+ turnover increased with age and development. The progressive change in resistance to osmotic stress is associated with a decrease in body surface area occupied by the relatively impermeable vitelline membrane and to the development of functional gills, leading to an increase in permeability to water and salt.