Winter response to salinity and nutritional fatty acids in juvenile striped bass (Morone saxatilis)

Since 2002, the Québec government has undertaken a major reintroduction program to re-establish striped bass Morone saxatilis (Walbaum, 1792), which had disappeared from the St. Lawrence River. As juveniles reach the estuarine portion of the St. Lawrence in their first winter, we tested the hypothesis that salinity and marine diet would improve their growth and thermal resistance during their first winter season. Juveniles were raised either in fresh (FW) or brackish water (BW, 14 ‰) and fed with a diet low in long-chain polyunsaturated fatty acids (LC-PUFA). a proxy of a freshwater trophic network, and a diet rich in LC-PUFA, a proxy of a marine trophic network. The mortality rate was higher in FW than in BW and hematocrit and liver mass were higher in FW than in BW juveniles. Diet significantly modified liver and muscle neutral fatty acid (FA) profiles: Σ saturated FA content was higher in marine diet fed juveniles while muscle polar oleic, linoleic, Σ mono-unsaturated, and Σn6 FA contents were higher in freshwater diet fed fish. Diet did not influence the effects of salinity on growth and survival, but juveniles fed on freshwater diet showed a greater thermal resistance than those fed with marine diet.