The Development of Fast-Start Performance in Fishes: Escape Kinematics of the Chinook Salmon (Oncorhynchus tshawytscha)

C-starts are high acceleration swimming movements critical for predator avoidance by fishes. Since larval fishes are particularly vulnerable to predation, C-start behavior is likely to be especially important during early life history stages. This paper examines the developmental changes in C-start performance with kinematic data on immature chinook salmon (Oncorhynchus tshawytscha) (eleuthroembryo stage, sensu Balon, 1975). The scaling of C-start kinematics of immature fishes differs from that of adults. Adult C-start durations increase with increasing body length while C-start durations of immature fishes decrease (e.g., adult stage 1 duration [sec] = 0.0019.length [L] [cm] $ 0.026 [R² = 0.77] [Webb, 1978]; eleuthroembryos stage 1 duration [sec] = −0.026L [cm] $ 0.100 [R² = 0.81]). Distance traveled during stage 2 also differs between adult and immature fishes. Adult distance traveled scales directly with length (distance [cm] = 0.38L^1.01 [cm], R² = 0.96 [Webb, 1978]) while chinook eleuthroembryo distance traveled is positively allometric with length (distance [cm]= 0.37L¹³¹ [cm], R² = 0.83). There are similarities in the development of C-starts and burst swimming. For example, mean velocity scales similarly between the two locomotor modes (For burst swimming: U_mean [cm/sec] = 8.1 ± 1.1L [cm] $ 4.89 [R² = 0.86] [Webb and Corolla, 1981]. For C-start stage 2: U_mean [cm/sec] = 10.96L [cm] - 14.09 [R² = 0.70]). This study demonstrates that C-start escape performance improves during early post-hatching development. Comparisons of immature chinook salmon fast-starts with data on larval burst swimming and on adult C-starts suggest that changes specific to developing fish affect the scaling of kinematic parameters.