Among six species Of juvenile fishes (<6 months old). stenohaline species (channel catfish Ictalurus punctatus and goldfish Carassius auratus) had their highest specific growth rate (G) and most efficient food conversion ratio (E-C) and energy absorption efficiency (I-E) in fresh water. Three of the euryhaline species (rainbow trout Oncorhynchus mykiss. striped bass Morone saxatilis and Gulf sturgeon Acipenser oxyrinchus desotoi) had higher G and had more efficient E-c and I-c in 3 and 9 parts per thousand salinities than in lower salinities (fresh water and 1 parts per thousand). For brown trout Salmo trutta (age3-4 months). 9 parts per thousand was above the optimum level for G and E-c, However. I-e for brown trout was not significantly different at 3 and 9 parts per thousand salinities. Over the salinity range tested. channel catfish had the largest change in G, E-C and I-E, while changes for euryhaline species were relatively small. Although all species tested survived and grew in all treatments, salinities its low as adversely affected the stenohaline species. and adversely affected brown trout. (C) 2001 The Fisheries society of the British Isles.