Fast-starts are high powered events of short duration, used by fish for prey capture and escape from predation. Here, the energetic cost of fast-starts in escape and prey capture for a fast-start specialist, the northern pike, Esox lucius, are determined and physiological and behavioural constraints assessed. This is done by comparing costs with literature values for physiological limits set my muscle mechanics and biochemistry, and comparing costs with other components of the energy budget. The combination of high speed film analysis (200-250Hz) and hydrodynamic models are used to determine the mechanical costs, hydrodynamic efficiencies and power output of fast-starts in prey capture (S-starts) and escape behaviour (C-starts). Excess post-exercise oxygen consumption (EPOC) is used to estimate the metabolic cost of fast-starts. A comparison of model predictions with required (acceleration) force estimates shows results are within 22% and similar to previous findings at lower film speeds. The caudal region including the caudal, dorsal and anal fins contribute the most to thrust (>90%) and the dorsal and anal fins contribute 28%. Due to the necessity for deceleration of fin sections during each tail beat, kinematics are not always optimal as predicted by the Weihs model. Mechanical power output, hydrodynamic efficiency and kinematic parameters (maximum velocities and maximum angle of attack of the caudal fin) are determined for fast-starts during prey capture and escape. Hydrodynamic efficiency averages 0.37 (range: 0.34 to 0.39) for C-starts and 0.27 (range: 0.16 to 0.37) for S-starts. The acceleration of added mass contributes the most to power output at 39%. Power output and efficiency for S-starts are more variable than C-starts and hydromechanical efficiency increases with number of tail beats for S-starts. Maximum muscle power output and maximum muscle stress during fast-starts in comparison to literature values for muscle function shows muscle power output during fast-starts is at its physiological limit but muscle stress is not. Metabolic efficiency is higher at 0.094 for C-starts than S-starts at 0.047. However, muscle efficiency estimates are similar averaging 0.252 for both fast-start types. Mean energetic cost of fast-starts is determined to be 26.5 J/kg for C-starts and 18.6 J/kg for S-starts. Based on the observation that pike can repeatedly fast-start up to 170 times before becoming exhausted and on estimates of available energy reserves from literature values for ATP and CrP concentrations in white muscle, the duration of fast-starts is concluded to not be limited by muscle physiology. Average power output is found to be similar for C and S-starts at 406 to 412 W/kg. Only hydrolysis of ATP and CrP can supply energy at this rate. Therefore, based on fish white muscle biochemistry and mechanics, power output during fast-starts appears to be limited by muscle physiology. The cost of fast-starts represents 0.03 to 2% of maintenance costs for pike and therefore only 5 to 30 fast-starts per day would be required to increase the daily energy budget by 10%. In addition, the cost of fast-starts represents 0.52 to 27.4% of surplus energy available from assimilated prey. Therefore, the cost of fast-starts can be significant and reducing fast-start duration is a probable strategy for minimising activity costs and thus increasing the energy available for growth or reproduction. / Science, Faculty of / Zoology, Department of / Graduate

Film is commonly used to estimate the fast-start performance of fish. An analysis of hypothetical, film-derived, and accelerometer-measured acceleration-time data of fish fast-starts indicates that the total error in film studies is the sum of the sampling frequency error (i.e., the error due to over-smoothing at low film speeds) and measurement error. The error in film based studies on the acceleration performance of fish is estimated to be about 33 to 100% of the maximum acceleration, suggesting that other methods of estimating acceleration should be employed. The escape performance of rainbow trout Oncorhynchus mykiss and northern pike Esox lucius (mean lengths 0.32 m and 0.38 m, respectively) were measured here with subcutaneously implanted accelerometers. Acceleration-time plots reveal two types of escape fast-starts for trout and three for pike. Simultaneous high-speed ciné films demonstrate a kinematic basis for these differences. Trout performing C-shaped fast-starts produce a unimodal acceleration-time plot (type I), while during S-shaped fast-starts a bimodal acceleration-time plot (type II) results. Pike also exhibit similar type I and II fast-starts, but also execute a second S-shaped fast-start that does not involve a net change of direction. This is characterized by a trimodal acceleration-time plot (type III). Intraspecific and interspecific comparisons of displacement, time, mean and maximum velocity, and mean and maximum acceleration rate indicate that fast-start performance is significantly higher for pike than for trout, for all performance parameters. This indicates that performance is related to body form. Overall mean maximum acceleration rates for pike were 120.2 ± 20 m s⁻² (x ± 2S.E.) and 59.7 ± 8.3 m s⁻² for trout. Performance values directly measured from the accelerometers exceed those previously reported. Maximum acceleration rates for single events reach 97.8 m s⁻² and 244.9 m s⁻² for trout and pike, respectively. Maximum final velocities of 7.06 m s⁻¹ (18.95 L s⁻¹, where L is body length) were observed for pike and 4.19 m s⁻¹ (13.09 L s⁻¹) for trout; overall mean maximum velocities were 2.77 m s⁻¹ for trout and 3.97 m s⁻¹ for pike. The fast-start performance of pike during prey capture was also measured with subcutaneously implanted accelerometers. Acceleration-time plots and simultaneous high-speed cin6 films reveal four behaviours with characteristic kinematics and mechanics. As for the escape data, fast-start types are identified by the number of large peaks that appear in the acceleration-time and velocity-time data. Comparisons of mean performance were made between each type of feeding fast-start. Type I fast-starts were of significantly (i.e., p < 0.05) shorter duration (0.084 s) and displacement (0.132 m) than type III (0.148 s and 0.235 m) and type IV (0.189 s and 0.307 m) behaviours, and higher mean and maximum acceleration (38.6 and 130.3 m s⁻², respectively) than the type II (26.6 and 95.8 m s⁻²), type III (22.0 and 91.2 m s⁻²), and type IV (18.0 and 66.6 m s⁻²) behaviours. The type II behaviours were also of shorter duration and displacement, and of higher mean acceleration than type IV fast-starts, and were of significantly shorter duration than the type LU behaviours. Prey capture performance was compared to escapes by the same individuals. When data are combined, regardless of mechanical type, mean acceleration (37.6 versus 25.5 m s⁻²), maximum acceleration (120.2 versus 95.9 m s⁻²), mean velocity (1.90 versus 1.57 m s⁻¹), and maximum velocity (3.97 versus 3.09 m s⁻¹) were larger, and duration shorter (0.108 versus 0.133 s) during escapes than during prey capture. No differences were found through independent comparisons of the performance of feeding and escape types II and III, but type I escapes had significantly higher mean velocity (2.27 versus 1.58 m s⁻¹), maximum velocity (4.70 versus 3.12 m s⁻¹), and mean acceleration (54.7 versus 38.6 m s⁻²) than the type I feeding behaviours. Prey capture performance was also related to prey size, apparent prey size (defined as the angular size of the prey on the pike's retina), and strike distance (the distance from the pike to the prey at the onset of the fast-start). Mean and maximum acceleration increased with apparent size and decreased with strike distance, while the duration of the event increased with strike distance and decreased with apparent size. No relation was found between the actual prey size and any performance parameter. Strike distance ranged from 0.087 to 0.439 m, and decreased as the apparent size increased from 2.6 to 9.9° (r² = 0.75). The type I behaviour was usually employed when the strike distance was small and the prey appeared large. As strike distance increased and apparent size decreased, there was a progressive selection of type II, then III, then IV behaviours. / Science, Faculty of / Zoology, Department of / Graduate