Date of Award

Fall 2020

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biology

Committee Chairperson

Frank E. Fish, PhD

Committee Member

Jennifer Maresh, PhD

Committee Member

Michael Rosario, PhD

Abstract

Scombrid fishes can attain exceptional swimming speeds due to their thunniform, lift-based propulsion, large muscle mass, and fusiform body shape. A rigid body restricts maneuverability for aquatic organisms. To test if turning maneuvers by the rigid-bodied Pacific bluefin tuna (Thunnus orientalis) are constrained, captive animals were video recorded from above as the animals routinely swam around a large circular tank or during feeding bouts. The turning performance was classified into three different types of turns: 1) glide turn, where the tuna uses the caudal fin as a rudder to passively move through the turn, 2) powered turn, where the animal uses continuous symmetrical strokes of the caudal fin to propel itself through the turn, and 3) ratchet turn, where the overall global turn is completed by a series of small local turns by asymmetrical stokes of the caudal fin. Individual points of the rostrum, peduncle, and tip of the caudal fin were tracked and analyzed using Tracker software. Frame-by-frame analysis showed that of the global turns, the ratchet turn had the fastest turn rate at all three points tracked, with a maximum of 301.76 deg s-1. During the ratchet turn, the peduncle exhibited a minimum global turn radius of 0.37m. However, the local turn radii were only 18.58% of the global ratchet turn. The minimum turn radii ranged from 0.38 m to 1.62m as a proportion of body length. Compared to the performance of other swimmers, the flexibility of the tail and mechanisms used by tuna does constrain turning performance.

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