Meeting Abstract

P2.140  Jan. 5  Roles of lateral keels and rows of scutes in passive trim control in swimming fishes GORDON, M.S.*; LAURITZEN, D.V.; WIKTOROWICZ, A.M.; Univ. of California, Los Angeles; Univ. of California, Los Angeles; Univ. of California, Los Angeles msgordon@ucla.edu

Trim control is important for swimming fishes. The better controlled their movements the greater their abilities to move as necessary. Trim control mechanisms affect posture, swimming trajectory, static and dynamic stability, and maneuverability. Mechanisms contributing to trim control are both passive and active. Passive mechanisms are both internal/structural (deriving from internal locations of centers of mass and buoyancy) and external/dynamic (based upon the use of hydrodynamic flows and forces). External/dynamic mechanisms derive mainly from morphological features, including body shapes and sizes and fin placements, shapes, and sizes. Integumentary armoring, ornamentation, and compliance properties are also significant. Active mechanisms derive mainly from patterns of body and fin movements. Variations in frequencies, amplitudes, coordination, and relative phasing of fin movements, also gait changes, occur as speed through the water varies. Different combinations of active trim mechanisms are used by fishes swimming in body and caudal fin (BCF) modes as compared with fishes using median and paired-fin (MPF) modes. This paper focuses on a hitherto largely neglected set of passive mechanisms of trim control. We discuss insights concerning passive mechanisms of trim control in a wide variety of other groups of fishes that derive from our earlier work with tetraodontiform fishes, specifically the armored tropical ostraciiform boxfishes and their relatives. Detailed consideration is given to roles of lateral keels and rows of scutes located on and near the caudal peduncles in many different elasmobranchs (sharks) and bony fishes.