Linking rates of metabolism and growth in marine fish larvae

Abstract

The intricate relationship between metabolism and growth is still largely unexplored in early life stages of fish. In the present study, two experiments were conducted to explore how standard metabolic rate (SMR) of Atlantic herring (Clupea harengus) larvae was related to differences in body size, growth rate and feeding environment. In two of the three trials of the first experiment, larval SMR decreased (up to 37%) after larvae experienced 3 days of sub-optimal feeding conditions. Inter-individual differences in SMR and nutritional condition (RNA–DNA ratio) were unrelated. In a second experiment, inter-individual differences in SMR were not explained by differences in short-term (otolith marginal increment width) or long-term (size-at-age, otolith diameter-at-age) growth indicators in well (ad libitum) fed larvae. Nevertheless, a negative relationship between SMR and otolith core diameter (formed between hatching and first feeding) was observed. In well-fed larvae, the relationship between SMR, temperature (T, 5–15 °C) and dry mass (DM, 60–3000 µm, 10–24 mm body length) was equal to: SMR = 0.0528 (± 0.0047) * DM 0.8859 (± 0.0127) * e T * 0.1046 (± 0.0034) [mean (± SE), adj R 2 = 0.9302, n = 384]. This is the first study to report the effects of DM on SMR in Atlantic herring larvae over a wide range of T. The present results suggest that metabolic flexibility can exist, particularly when larvae experience contrasting feeding environments, which needs to be taken into account when evaluating factors affecting larval growth and survival in the sea.