Effect of body size, temperature, and salinity on the routine metabolism of larval and juvenile spotted seatrout

Routine oxygen consumption rates of young spotted seatrout Cynoscion nebulosity (Sciaenidae) were measured over a range of temperatures (24, 28, 30 and 32 degreesC) and salinities (5, 10, 20, 35 and 45). Larvae and juveniles, 4(.)1-39(.)5mm standard length (L-S) ranging several orders of magnitude in dry body mass were used to estimate the mass-metabolism relationship. Oxygen consumption (mul O-2 larva(-1) h(-1)) scaled isometrically with body mass for larvae <5-8 mm L-S (phase I, slope = 1(.)04) and allometrically thereafter (phase II, slope = 0(.)78). The inflection in the mass-metabolism relationship coincided with the formation of the hypural plate and an increase in the relative tail size of larvae. Salinity did not have a significant effect on routine metabolism during phase I. Temperature and salinity significantly affected routine metabolism during phase II of the mass-metabolisin relationship. The effect of salinity was temperature dependent, and was significant only at 30degreesC. Response surfaces describing the environmental influences on routine metabolism were developed to provide a bioenergetic basis for modelling environmental constraints on growth. (C) 2004 The Fisheries Society of the British Isles.