Energy utilization during swimming and cost of locomotion in larval and juvenile fish

Abstract

Summary Oxygen consumption and ammonia excretion rates increased in an accelerated manner in larvae and juveniles of whitefish (Coregonus sp.) as a function of swimming speed. The three-dimensional patterns of fish metabolic rates (expressed as energy consumed or nitrogen excreted) versus body weight and swimming speed show that the total standard metabolic rate (i. e. at extrapolated zero swimming speed) increased during early life of whitefish, followed by the expected decrease. This phenomenon might be due to the profound changes in oxidative and glycolytic enzyme activities during fish “metamorphosis”. Standard metabolic rate of ammonia excretion, as a principal product of protein catabolism in fish, decreased by one order of magnitude in early coregonid ontogenesis. This means that protein utilization as an energy source decreases as far as standard metabolism is concerned, but increases with swimming speed. This trend is opposite that in adult fish, where protein utilization in the overall energy supply is diminished at increasing swimming speed. The cost of locomotion offish larvae and juveniles demonstrates that the energy expenditure increases logarithmically with decreasing fish size but at an accelerated rate as compared to adult fish. This contradicts earlier estimates of lower cost of swimming in fish larvae than cost of paddle-propulsion swimming in small invertebrates or cost of flying in insects.