Hopkins Marine Station Student Paper

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(full paper is archived in the Miller Library)

Title: The center of buoyancy and fin use in the equilibrium of the rockfish Sebastes atrovirens
Student Author(s): Kutner, Lynn
Faculty Advisor(s): Denny, Mark
Pages: 30
Location: Final Papers Biology 175H
Date: June 1989
Keywords: nearshore fishes
Abstract: The kelp rockfish (Sebastes atrovirens) hovers at a range of angles to horizontal using slow movements of its pectoral and caudal fins. It adjusts its buoyancy using a swimbladder, which increases the volume of the fish without increasing its mass and thus reduces its net density. I found that the center of buoyancy, the point at which the force due to the swimbladder acts, is anterior and ventral to the center of gravity. This creates rotational instability. I formed a model to examine the effects of the buoyant force, the force due to gravity, and the forces of the pectoral and caudal finds on the rotational and vertical translational equilibria of the fish. I found that the net torque is much more sensitive to changes in the angle of teh fish than is the net vertical force.