Effects of various levels of dietary protein on survival, molting frequency and growth of juvenile blue crabs ( Callinectes sapidus)

An 18-week study was conducted to examine growth characteristics of the juvenile blue crab ( Callinectes sapidus Rathbun) fed various levels of dietary protein. Hatchery raised individuals (157) of identical age (160 days) from the same gravid female were assigned to one of four dietary treatments: adult brine shrimp ( Artemia salina Leach) and artificial pelleted diets containing crude protein levels of 23, 37, and 49%. Growth rate, measured as a function of mean weight and mean carapace width, indicated that brine shrimp-fed crabs were larger ( P < 0.05) than crabs fed artificial pelleted diets. Also, blue crabs fed either 37 or 49% crude protein were larger than crabs fed the 23% crude protein diet. Molting frequency was greater in the brine shrimp-fed crabs than in those fed the artificial diets. No differences in growth were detected when comparing males vs. females fed the artificial diets. However, females demonstrated greater growth than males within the brine shrimp treatment. Protein concentration of freeze-dried whole blue crab carcasses was greater in brine shrimp-fed crabs than in crabs fed the artificial pelleted diets ( P < 0.05).