Energetics of swimming in fishes using different methods of locomotion: I. Labriform swimmers

The patterns relating rates of oxygen consumption to steady sustained and prolonged swimming at different speeds were determined in adults or near adults of two species of marine fishes that use the labriform mode of swimming (labriform swimmers). Effects of acute temperature changes on these patterns were measured. Species were the shiner surfperch,Cymatogaster aggregata and the señorita wrasse,Oxyjulis californica.Metabolic data were analyzed three different ways. The first (method of Brett) was based upon mass specific oxygen uptake and length specific swim speed; data in this form were analyzed both as best-fit power functions and as the mathematically equivalent least squares linear regressions for semi-log plots. The second and third methods were based upon drag based hydromechanical theory concerning power requirements for swimming in fishes: total metabolic ratesvs. absolute swimming speeds, analyzed both as best-fit power functions and least squares linear regressions for log-log plots.The main finding, demonstrated by all three methods of calculation, was that the slopes of all regression lines (both semi-log and log-log) and the exponents of almost all power functions (five out of six) were very low. The Brett method applied to subcarangiform swimmers usually produces slopes averaging 0.36 (using base-10 logarithms). The slopes calculated by that method in the present study were 0.02-0.08. Low slope values could result from the interactions of many factors. Additional data are needed to determine which combinations of factors actually produced them. On this basis metabolic rate data on intact labriform swimmers, by themselves, appear unusable as empirical tests of theory based predictions concerning power requirements for fish swimming.