Bioenergetics of marine teleosts during early life stage

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The relationship between metabolism of an individual fish M and body mass W is expressed by an allometric equation M=aW^b. Mass-exponent b is smaller than unity, because mass-specific metabolic rate M/W usually decreases with increasing body mass. However, we have not enough information about this relationship during the early life stages of teleosts, In this study, we examined ontogenetic change in the metabolism-body mass relationship with three teleosts.Oxygen consumption of intact fish M_< in vivo>, that of chopped fish M_< in vivo>, and ammonia excretion were determined with ayu Plecoglossus altivelis altivelis (0.00043-0.41 g in wet body mass), tiger puffer Takifugu rubripes (0.00068-2.7 g) and croaker Nibea japonica (0.00025-10 g) at 20ﾟC.M_< in vivo> was determined using one of closed, semi-closed or constant flow respirometry, M_< in vivo> a volumetric respirometry, and ammonia excretion rate an absorptimetry.Mass-specific metabolic rate of intact fish M_< in vivo> /W of ayu was almost constant independent of body mass from just after hatch (0.00043 g) to 30 days old (0.04 g), then decreased. While, M_< in vivo>in /W of ayu decreased with growth immediately after hatch with a monophasic negative allometry. M/W both in vivo and in vitro of puffer and croaker increased with growth during a week after hatch with virtually unchanged body mass, then decreased with increasing body mass with several phases. In these phases, a-value in M=aW^bb increased with transfer of developmental stage. The difference of ontogenetic change of metabolism among three species can be attributed to the difference of extent of organogenesis just after hatch. The increase of a-value with growth in puffer and croaker is considered to reflect morphological and ecological changes with growth.