Measuring Metabolic Rates of Marine Fish Larvae: Progress and Challenges

Metabolic costs are extremely high in young marine fish larvae and knowledge on how intrinsic and extrinsic factors affect metabolic costs (and how best to estimate those costs) is important if we hope to understand environmental constraints on early growth and survival. We provide an historical perspective on measurements of respiration rates in larvae of marine fishes and perform a meta-analysis of results (measurement methods, metabolic rates, ontogenetic changes, taxonomic differences) obtained from 51 studies examining 50 species from 25 families. Standard (anaesthetized or darkness), routine and active respiration rates were reported in 15, 95 and 10% of the studies, respectively, and much more work has been performed on larvae of temperate (80%) compared to tropical (14%) and polar (4%) species. More than 35% of the studies have been published since 2000 owing to both advancement in oxygen sensors and the growing emphasis on understanding physiological impacts of environmental change. We recommend common protocols to facilitate cross-taxa comparisons such as the effect of temperature (Q₁₀ 1.47 to 3.47), body mass (slope of allometric changes in R from 0.5 to 1.3), and/or activity level on metabolic costs as measured via respiration rate.