The Design and Implementation of Mechanical Tests Aboard the SSV Robert C. Seamans and an Analysis of the Mechanical Properties of Thunniform and Carangiform Backbones

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While correlations between body stiffness and swimming form have been extensively studied, it has yet to be determined whether fish backbones are themselves adapted for their swimming modes. A better understanding of the mechanical properties of fish backbones will greatly augment our knowledge of the biological and physical factors that contributing to overall body stiffness. This study used two different tests to analyze the properties of fish backbones. A tensile test was used to examine how elastic moduli, vary along their length. A cantilever bending test was used to compare the stiffness of backbones of different species and different swimming forms. The tensile test was performed on a Skipjack Tuna, with the initial expectation that the anterior region would show the least elasticity because it is its rigidity that forms the basis of thunniform swimming. It was found that the anterior and posterior regions of the backbones were much more rigid then the middle. Ostensibly this is because neither does the need to be stiff to support the rigid structure of thunniform swimming as in the anterior end nor is it prone to the repetitive, (material) fatigue inducing movement as is the posterior end. The cantilever bending test was perform on a Yellowfin Tuna, a Mahi Mahi, and two Skipjacks. While the results from the Skipjacks were inconclusive due to significant differences in size, results from the Yellowfin and Mahi Mahi supported the original hypothesis that thunniform swimmers will show a greater overall stiffness in their backbones in order to decrease the energetic requirements for a swimming form that keeps lateral movement to the posterior 10% of their body.


Type of resource text
Date created June 12, 2009


Author Kratschmer, Christina


Subject Stanford@SEA
Subject S-223
Subject Hopkins Marine Station
Subject Department of Biology
Subject Department of Earth System Science
Subject BIOHOPK 182H
Subject BIOHOPK 323H
Subject EARTHSYS 323
Subject ESS 323
Subject body stiffness
Subject swimming
Subject backbone
Subject mechanical properties
Subject fish
Subject elastic modulus
Subject bending
Subject tensile
Subject skipjack
Subject tuna
Subject fatigue
Subject yellowfin
Subject mahi mahi
Genre Student project report

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Kratschmer, Christina. 2009. The Design and Implementation of Mechanical Tests Aboard the SSV Robert C. Seamans and an Analysis of the Mechanical Properties of Thunniform and Carangiform Backbones. Unpublished Student Work, S-223, Stanford@SEA, Stanford Digital Repository.


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