MUSCLE POWER OUTPUT LIMITS FAST-START PERFORMANCE IN FISH

Fast-starts associated with escape responses were filmed at the median habitat temperatures of six teleost fish: Notothenia coriiceps and No tothenia rossii (Antarctica), Myoxocephalus scorpius (North Sea), Scor paena notata and Serranus cabrilla (Mediterranean) and Paracirrhites f orsteri (Indo-West-Pacific Ocean). Methods are presented for estimatin g the spine positions for silhouettes of swimming fish. These methods were used to validate techniques for calculating kinematics and muscle dynamics during fast-starts, The starts from all species show common patterns, with waves of body curvature travelling from head to tail an d increasing in amplitude. Cross-validation with sonomicrometry studie s allowed gearing ratios between the red and white muscle to be calcul ated. Gearing ratios must decrease towards the tail with a correspondi ng change in muscle geometry, resulting in similar white muscle fibre strains in all the myotomes during the start. A work-loop technique wa s used to measure mean muscle power output at similar strain and short ening durations to those found in vivo. The fast Sc. notata myotomal f ibres produced a mean muscle-mass-specific power of 142.7 W kg(-1) at 20 degrees C, Velocity, acceleration and hydrodynamic power output inc reased both with the travelling rate of the wave of body curvature and with the habitat temperature. At all temperatures, the predicted mean muscle-mass-specific power outputs, as calculated from swimming seque nces, were similar to the muscle power outputs measured from work-loop experiments.