Meeting Abstract
Invasive Silver carp are thriving in eutrophic environments in the United States due to efficient filter-feeding mechanisms. Like many filter-feeding fishes, Silver carp utilize modified gill rakers to enhance filtering efficiency; however, unlike other fishes, Silver carp gill rakers are fused together to form highly porous, channeled filtering plates. This morphology can capture particles ranging in size from 4-80 µm, which may explain how this species can outcompete other fishes. While descriptive studies exist no work has yet discovered the mechanism behind Silver carp filtration. Here we investigate the hydrodynamics of Silver carp filter feeding using volumetric Particle Image Velocimetry (3D PIV). Fixed gill rakers and 3D models based on 10µm and 28µm µCT scans of adult Silver carp and its sister species Bighead carp were placed in a recirculating flow tank with water flowing across the model in both the anteroposterior and posteroanterior directions. Neutrally-buoyant 50µm nominal size particles were illuminated by a 50mJ-100Hz Nd:YAG pulse laser focused into a 14cm x 14cm x 14cm volume using an optic and mirror system, tracked and processed using V3V software, and resulting vector information was analysed in Tecplot. Using 3D PIV, we tracked particle and fluid interaction from the surface of the gill raker through the various sized pores along the filter. Based on results from multiple PIV studies and morphological analyses, we suspect that the morphology on the outer face of the gill raker plates and the orientation of those openings increases the vorticity of water as it moves across the the gill rakers, accounting for particle capture and retention.
