Energetic cost of sustained swimming in the late pelagic stages of reef fishes

The late pelagic stages of reef fishes are capable of swimming substantial distances which may significantly modify their dispersal. The energetic cost of this swimming, at 13.5 cm s(-1), was measured for the late pelagic stages (mean total length ranging from 10.8 to 22.4 mm) of 9 species from 4 reef fish families (Pomacentridae, Pomacanthidae, Chaetodontidae and Lethrinidae). Of the potential sources of energy (lipid, carbohydrate and protein), all were utilised, but lipid appeared to be the most energetically important across the species. Lipid levels decreased significantly in 5 of the 9 species. The decrease and the relative percentage of energy lost in the form of Lipid was greater than for carbohydrate and protein. The pattern of energy utilisation varied among species. The greatest decrease in energy stores was seen in the heaviest species, which swam for the longest duration (the chaetodontids and lethrinid), showing up to 72% decrease in lipid, 66% decrease in carbohydrate and 39% decrease in protein. The Lighter species, which swam for shorter time periods (the pomacentrids and the pomacanthid), showed comparatively little change in energy reserves after swimming. Initial levels of energy reserves correlated with distance swum and were greatest in the heavier species.