AGE-LINKED CHANGES IN SALINITY TOLERANCE OF LARVAL SPOTTED SEA-TROUT (CYNOSCION-NEBULOSUS, CUVIER)

Acute salinity tolerance limits for the estuarine spawning spotted seatrout, Cynoscion nebulosus (Cuvier). were evaluated by examining 18 h survival of larvae in an extensive range of salinity treatments (0 to 56 ppt). Larvae from eggs spawned in two different salinities (24 and 32 ppt) as well as larvae acclimated in hypersaline and brackish waters were compared. Both upper and lower salinity tolerance limits showed an age‐linked pattern, decreasing to a minimum tolerance range (6.4 to 42.5 ppt) at age 3 days after hatching (at 28o C) and increasing to the widest range tolerated (1.9 to 49.8 ppt) on the last day tested (age 9 days). Acclimation to hyposaline conditions was demonstrated by larvae spawned at 32 ppt although significant hypersaline acclimation could not be demonstrated. Altered upper limits to the range tolerated by larvae from different spawning salinities indicated parental and/or early acclimation effects are important. Consistently greater vulnerability to both hyper‐ and hyposaline conditions at age 3 days after hatching was observed in all tests conducted. Exposures related to the onset of feeding at this time are likely explanations for this reduced tolerance. Copyright © 1991, Wiley Blackwell. All rights reserved