Sprint Swimming Performance of Juvenile European Sea Bass

—Despite its potential for determining animal success in a variety of ecologically important situations, very little is known about the sprint swimming performance of fishes. To evaluate whether selection on sprint swimming performance occurs in the wild, one must first demonstrate measurable and reproducible variation of sprint performance. In this study, we employ a computercontrolled laser detection system to study the sprint performance of 75 juvenile European sea bass Dicentrarchus labrax raised under uniform conditions in the laboratory. This percichthyid is a prized sport and food fish in Europe and similar ecologically to the North American striped bass Morone saxatilis. Individual European sea bass were subjected to endurance swimming performance tests and had their active metabolic rates measured to test hypotheses concerning relationships between these measures and sprint performance. Maximal velocity obtained by an individual during repetitive sprint performance trials was very reproducible but varied substantially among individuals. Consecutive sprint trials with an individual revealed that maximal capacity for sprinting could only be ascertained through multiple trials (at least four). The sprint performance test described in this study should be useful for large-scale studies in which investigators desire performance information on a large number of animals relatively quickly. However, active metabolic rate measurements and an endurance test were not considered effective performance measures for juvenile European sea bass, and there was no relationship between sprint swimming performance and either of the tests. Different types of swimming performance are required by some fishes to successfully reach their reproductive potential (Reidy et al. 2000; Nelson et al. 2002). Predator–prey interactions generally last a few seconds and test the operation of neuronal pathways encompassing processes from sensation through activation of the neuromuscular junction as well as testing the twitch contraction kinetics of muscle performing at maximal power output. In contrast, migrations will tax the fish’s ability to sustain aerobic muscular contractions for days. Despite this diversity of demands placed upon the swimming apparatus of fishes, the vast majority of studies on fish swimming performance use only a single trial of a single swimming test to assess locomotor performance (see Beamish 1978 for a review; Hammer 1995; Plaut 2001; Nelson et al. 2002). In addition, few studies have examined performance between the scales of starting from a dead stop (‘‘fast-start performance’’) and long-distance swims (critical swimming and en* Corresponding author: [email protected] Received May 25, 2004; accepted April 18, 2005 Published online August 29, 2005 durance tests). If successful inference is ever to be made about the role of locomotor performance in determining success of fish in the wild, multiple performance tests mirroring the types of swimming required in nature must be employed (locomotor performance space: Bennett and Huey 1990; Nelson et al. 2002). This study examines sprint swimming performance in a cohort of juvenile European sea bass Dicentrarchus labrax, an economically important fish in western Europe. This percichthyid is ecologically similar to its confamiliar, the North American striped bass Morone