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Fishery Bulletin 94(4), 1996 



(ATP) generated by aerobic metabolism must be used 

 for growth in a normal, developing individual. The 

 fraction of aerobic metabolism that generates the ATP 

 for biosynthesis is the increase in metabolism fol- 

 lowing feeding variously known as specific dynamic 

 action (SDA) (Kleiber, 1961), specific dynamic effect 

 (Kleiber, 1967), or heat increment (Brett and Groves, 

 1979). Thus, diets that promote high growth induce 

 high energy use as SDA. Jobling's view conflicts with 

 the more traditional idea that growth and SDA are 

 in direct competition for ingested energy. 



The 40% to 60'7r reduction in metabolic rates of 

 starved individuals indicates that feeding metabo- 

 lism (SDA) is a substantial fraction of the daily meta- 

 bolic costs above maintenance in fed larvae. Because 

 SDA is specifically related to growth, and individu- 

 als growing slowly demonstrate little change in meta- 

 bolic rate following feeding (Jobling, 1985), it follows 



that the large reduction in metabolic rate of starved 

 red drum is indicative of a rapidly growing fish. 



Nitrogen excretion 



Our data on nitrogen excretion are the first reported 

 for larval red drum; they add significantly to the very 

 limited information describing excretion in fish lar- 

 vae. Absolute ammonia excretion rates of red drum 

 larvae (Table 3; Fig. 3) were similar to those reported 

 by Klumpp and von Westernhagen (1986) for simi- 

 lar size Pleuronectes platessa (0.025-0.050 jig NH.,/ 

 ind./h at 100 ng and 11 d) and Blennius pavo (0.05- 

 0.10 ng NH.j/ind./h at 100 iig and 5 d). 



The 50 c / ( drop in absolute and mass-specific am- 

 monia excretion with starvation (Table 3; Figs 3 and 

 4) mirrors the drop observed in oxygen consumption 

 rate, indicating a general slow-down in metabolic 



