GIBB, A.C.; LIU, C.*; WESP, H.M.; SWANSON, B.O.; Northern Arizona University: What is the functional basis of improved escape performance during early development in the rainbow trout?

For many fishes, most mortality occurs during the larval period. Thus, the ability to produce an escape response during this time may be critically important to individual fitness. Previous research has shown that rainbow trout, Oncorhynchus mykiss, escape response performance improves (i.e., individuals become absolutely faster) throughout early post-hatching development. In this study, we examine the functional basis of this improvement by testing the general hypothesis that developmental changes to the musculoskeletal system allow improved performance. In the first phase of this study, we assessed changes in behavior across development by recording high-speed digital images of rainbow trout performing escape responses and analyzing the kinematics of the body. We measured bending of the vertebral column during the escape response in three ways: (1) the coefficient of curvature (the bent vertebral chord length divided by the straight vertebral column length), (2) the bending produced at consistent intervals along the body (10%, 20%, etc.) and (3) inter-vertebral bending (the bending produced between any two adjacent vertebrae). Our preliminary results reveal that rainbow trout produce a large degree of bending during early development, and this bending decreases as the trout grow older and larger. For example, the coefficient of curvature suggests that newly-hatched trout produce twice as much bending as juvenile trout. We propose that changes to the musculoskeletal system during development produce increased axial stiffness, which in turn allows the production of a more effective response. Research is currently underway to address the specific morphological changes that produce the observed differences in kinematics and increase in escape performance.