Predation on Pseudodiaptomus annandalei (Copepoda : Calanoida) by grouper fish larvae Epinephelus coioides under different hydrodynamic conditions ?
Résumé
Environmental conditions such as illumination, hydrodynamics, and densities of organisms affect behavior ofboth, fish fry and their prey with impacts on trophic interactions in ecosystems and aquaculture management alike. The present study demonstrated that the copepod Pseudodiaptomus annandalei perceived juvenile fry of the grouper Epinephelus coioides as predators and exhibited escape reactions mediated mainly by physical and/or chemical signals. Under illumination, prey capture rates were significantly greater (pb0.01, Mann-Whitney U test) at moderate turbulence (747±104 individuals/h, n=3) than in calm water (597±76 individuals/h, n=3). The maximum darting speed of copepods in response to sensing fish fry in calm water was significantly greater (one-way ANOVA, pb0.05) than that in either turbulent or enhanced flow conditions, indicating that the ability of copepods to escape from predators was greater in calm water than in turbulent water or enhanced flow conditions. The maximum number of copepods eaten by the fish larvae increased in slow and medium hydrodynamic turbulence compared to either calm water or strong turbulence, suggesting that intermediate levels of turbulence favor predatory larvae.