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 predato r avoidance by fishes. Since larval fishes are particularly vulnerable to predation, C-start behavior is likely to be especially important d uring early life history stages. This paper examines the developmental changes in C-start performance with kinematic data on immature chinoo k 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 [R(2) = 0.77] [Webb, 1978]; eleuthroembryos stage 1 duration [sec] = -0.026 L [cm] + 0.100 [R(2) = 0.81]). Distance traveled during stage 2 also d iffers between adult and immature fishes. Adult distance traveled scal es directly with length (distance [cm] = 0.38L(1.01) [cm], R(2) = 0.96 [Webb, 1978]) while chinook eleuthroembryo distance traveled is posit ively allometric with length (distance [cm] = 0.37L(1.31) [cm], R(2) = 0.83). There are similarities in the development of C-starts and burs t swimming. For example, mean velocity scales similarly between the tw o locomotor modes (For burst swimming: U-mean [cm/sec] = 8.1 +/- 1.1L [cm] + 4.89 [R(2) = 0.86] [Webb and Corolla, 1981]. For C-start stage 2: U-mean [cm/sec] = 10.96L [cm] - 14.09 [R(2) = 0.70]). This study de monstrates that C-start escape performance improves during early post- hatching development. Comparisons of immature chinook salmon fast-star ts with data on larval burst swimming and on adult C-starts suggest th at changes specific to developing fish affect the scaling of kinematic parameters.