EFFECTS OF DIETARY BETAINE AND SODIUM-CHLORIDE ON SEAWATER ADAPTATION IN ATLANTIC SALMON PARR (SALMO-SALAR L)

1. Parr in freshwater were fed supplementary betaine (1.5%) and/or NaCl (10%) from 27 September to 21 October, then directly transferred to seawater. 2. Dietary betaine resulted in a 5-fold increase in muscle betaine content, but had no significant effect on either growth, or the degree of iono/osmotic imbalance following transfer to seawater. 3. NaCl reduced growth rate, but stimulated gill Na+-K+-ATPase activity, and significantly reduced the degree of osmotic stress following transfer to seawater.