Predator-prey interactions under calm and turbulent conditions: experimental studies on planktivorous fish

• Main Authors: Mohamed-Sofiane Mahjoub, 蘇菲恩
• Other Authors: Jiang-Shiou Hwang
• Format: Others
• Language: en_US
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/05853762641644115685

博士 === 國立臺灣海洋大學 === 海洋生物研究所 === 98 === In this thesis experimentally investigated predator-prey interactions between larval and juvenile fish with their planktonic prey. At first, we conducted small-scale predation experiments to investigate the flexibility of fish larvae search behavior as well as the effect plankters’ swimming behavior on the predator-prey interaction. 2D and 3D video techniques were used to investigate parameters such as the ingestion rate and the capture success at the individual level. Swimming patterns of both predators and preys were quantified using both scale-dependent (Speed, acceleration, fixation distance, net to gross displacement ratio) and scale-independent (Fractal dimension, multifractal analysis) metrics. Results revealed that fish larvae switch from an anistropic multifractal search pattern in absence of prey to an isotropic spatially-restricted search behavior when food is present. We also demonstrated that swimming behavior not only governs encounter rates but also the capture success. In fact, less complex pursuits associated to attacks from shorts distances yield highest capture success. The investigation of the effect of prey swimming behavior on the vulnerability to predation corroborated previous theoretical studies that faster preys are more conspicuous to predation than slower ones. In a second part of this work, larger scale experiments aiming at the elucidation of the effects of turbulence on feeding success of fish larvae offered realistic prey densities. The results of gut contents analysis of fish feeding under increasing turbulence levels revealed that turbulence has negative effects on the feeding rates and maximum food intake of planktonic predators when preying on a non-evasive prey (Artemia). Conversely, when feeding on an evasive prey (live copepod), moderate turbulence was beneficial to fish.