Effects of diet and environmental salinity on the growth, mortality, and tissue structure of juvenile striped bass

Juvenile striped bass Morone saxatilis (approximately 60 d old) were fed either a commercial trout feed or an open-formula salmon feed for 16 weeks and reared in 24°C fresh water or saline water prepared from sodium chloride or synthetic sea salt. Fish that were fed salmon feed were larger, contained higher levels of body lipid, and had livers with uniform glycogen vacuolation. Fish that were fed trout feed were smaller, contained less body lipid, and had necrotic liver tissue. More than 95% of the fish fed the trout feed and reared in water containing sodium chloride at 10‰ salinity died within the first 2 weeks. Mortality of fish fed the salmon feed under the same rearing conditions was 3% in 2 weeks. An osmoregulatory dysfunction from an imbalance of environmental calcium and sodium is suggested as the cause of the mortality. Although no definitive cause was established for the diet-related histological changes in the livers of fish that were fed the trout feed, type and level of dietary essential fatty acids are suspected