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How Juvenile Flounders Swim: Body and fin kinematics of free swimming juvenile flounders

Oostveen, M.M. van (2003) How Juvenile Flounders Swim: Body and fin kinematics of free swimming juvenile flounders. Master's Thesis / Essay, Biology.

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Flounders (Platichthysflesus) have a body geometry, which is adapted to a life on the sea bottom. When swimming the dorso-ventrally flattened body makes the flatfish to undulate its body vertical to the substratum. In addition the flounders use their dorsal and anal fin for propulsion as well, which stands in contrast to round fish. Due to the lack of a hydrostatic organ, flounders are heavier than water and need to produce lift while swimming. For this study, it was expected that flounders show significant differences in swimming kinematics compared to round fish. Comparison of the body and fin movements of the flounders was desirable to show a relation of the two propulsion systems. Juvenile flounders were filmed in side view at 125 frames s-1 while swimming freely towards a food source. For analysing the wave characteristics of the undulatory movements, ten points on the upper body side, fifteen on the fin tip and fifteen points on the fin base were followed in time. Cubic splines were fitted through these points, to yield accurate estimates of the wave characteristics. The obtained lines indicate the movements of the body and the fin in space and time. Kinematic data were obtained following the methods of Videler and Wardle (1978). Three film sequences showing upward swimming of three different juvenile flounders were analysed. The following results were found: - The last two third of the body of all flounders were active, having about 1 to 1.2 waves at once. - The fins were undulating over the whole length, with 1.5 to 1.9 waves at one time. - For the body the amplitude maximum was located at the tail. - For the fin, the maximum amplitude was found half way to two third of the fin length. - Differences were seen within and between the flounders in the tail beat amplitudes. - An interpretation was given about a possible steering component of the tail beat direction. - Wave speeds v varied quite strongly within and between the flounders. It indicated that the flounders have possibilities to alter their swimming style and are able to change quickly between wave speeds during swimming. - Differences in swimming movements of flatfish compared to round fish were: a smaller wave length lambda b, stride length lambda s and swimming efficiency, which make flounders bad forward swimmers. - The waves on the fins are not an artefact of the moving body, but the flounders appear to have two propulsing systems, the body and the fins. - The fins are moving in phase with the body, enlarging the moving surface and the effect of the waving propulsion. - Small differences in the movements are explained as complexity of the moving systems and can serve as steering components and stabilising factors.

Item Type: Thesis (Master's Thesis / Essay)
Degree programme: Biology
Thesis type: Master's Thesis / Essay
Language: English
Date Deposited: 15 Feb 2018 07:31
Last Modified: 15 Feb 2018 07:31

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