Larval spotted seatrout (Cymoscion nebulosus) grew faster on 1 and 2 day prefed brine shrimp (Artemia salina) nauplii than fish fed newly-hatched nauplii. Fish growth and survival were reduced when 3 and 4 day pref.ed, as compared with newlyhatched nauplii were offered. Proximate analysis and calorimetry demonstrated the occurrence of a temporal decline in the nutritional value of both fed and unfed brine shrimp nauplii. At the relatively low levels of algal cell concentration available for prefeeding brine shrimp, this study indicates that I day old unfed nauplii are nutritionally equal to algae prefed nauplii as a food source for larval spotted seatrout. One day old brine shrimp nauplii are a better food organism for larval spotted seatrout 12 to 21 days of age than newly-hatched nauplii because of the larger size of the former.