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Buoyancy regulation in sharks: The importance of the fins and body

Groot, B. de (2010) Buoyancy regulation in sharks: The importance of the fins and body. Bachelor's Thesis, Biology.

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When discussing the buoyancy of sharks, it is important to understand the hydrodynamics that are of influence. In this paper I shall discuss this hydrodynamic component, paying special interest to the role of the heterocercal tail, the pectoral fins and the body as a lifting surface. I conclude that the classical model of the heterocercal tail exerting a force directed above the centre of mass is partly correct. Indeed, the force exerted by the caudal fin causes thrust and lift and a subsequent torque. However, the view of the pectoral fins as balancing this torque appears to be incorrect for certain shark species, most notably the leopard shark. It appears the body itself counters this torque by being tilted at a positive angle of attack during steady horizontal swimming. The pectoral fins are used to initiate pitching movements during rising and sinking behaviour. I support the adapted classical model of force balance Wilga and Lauder (2000) proposed, based on these findings. However, although this model is likely to prove useful when discussing leopard sharks or similar species, it should not be carelessly applied to dissimilar species, such as pelagic sharks. As these sharks have not been observed to swim with their bodies tilted at a positive angle of attack and due to the shape of the ventral body, one should not assume these sharks use their bodies in the same hydrodynamic way as do leopard sharks. The use of the pectoral fins as lifting surfaces also can not be ruled out, until proper research is conducted. However, I do argue that Wilga and Lauder’s (2000) model should be used as a new standard, replacing the classical model, and should continue to evolve as data on other shark species become available. Research in this field should expand to include shark species other than leopard sharks or similar species, in order to provide the necessary data to improve this model and compose an adapted model, which can be applied to a wider variety of species.

Item Type: Thesis (Bachelor's Thesis)
Degree programme: Biology
Thesis type: Bachelor's Thesis
Language: English
Date Deposited: 15 Feb 2018 07:44
Last Modified: 15 Feb 2018 07:44

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