SPECIFIC DYNAMIC ACTION, GROWTH AND DEVELOPMENT IN

The larval stage of marine fish is a period of rapid growth and development. Atlantic cod (Gadus morhua) are approximately 4-5 rnm in length upon hatch and feed endogenously from their yolk sac for the first week. After this time, larval cod must successfully capture live prey to survive and to fuel high growth rates of greater than 10%d". Previous studies have found that during exogenous feeding and at growth rates greater than 8%d1 larvae experience what appears to be cost free growth, where mass specific metabolic rate does not decrease with increasing mass. Due to size and condition constraints involved in working with larval marine fish, few data exist on the metabolism of early larval growth. This study was done using microcalorimetry to identify specific dynamic action (SDA) which represents the cost of feeding, digestion, and protein assimilation (growth) in larval cod. Cod were used in the experiments only after the yolk sac was completely utilized, and the larvae were feeding exogenously. This study was the first to record changes in metabolic rates as a function of feeding in larval fish using a microcalorimeter. Growth rates for two populations (Rhode Island and Newfoundland) of Atlantic cod were measured and ranged from 6.9%d- ' to 13. l%dml, showing that larva