Meeting Abstract

83.4  Tuesday, Jan. 6  Estimating the ram suspension feeding efficiency of elasmobranchs PAIG-TRAN, Misty EW*; STROTHER, James A; SUMMERS, Adam P; Univ. of California at Irvine; Univ. of California at Irvine; Univ. of California at Irvine epaig@uci.edu

Filter feeding fishes consume vast numbers of tiny (5-3000 microns) prey by filtering immense quantities of water through their oropharyngeal cavity. Differential anatomies between cartilaginous and bony fishes suggest differences in suspension feeding mechanisms. Models of ram suspension feeders (e.g. herring, mobulas, etc) suggest that the gill rakers likely function either as a self cleaning sieve (cross-flow filtration) or as a sticky filter to separate food particles from the egressing water. To understand the role morphology and fluid flow play on particle retention in a typical ram suspension feeder, we measured the filtration efficiency in a simple physical model. We varied the buccal length, flow speed and the architecture of the gills slits; including the number, size, orientation and pore size/permeability of the model. Models were placed in a recirculating flow tank with plankton-like particles (40-2000 microns) collected at the esophagus and at the gill rakers to locate the highest density of particles accumulation. Changing the number of gills resulted in a change in the filtration mechanism of particles from a type of notch filtration, with mostly very small (less than 50 microns) and very large (above 1000 microns) particles collected, to a band pass type filter, with primarily intermediate sized particles (100-1000 microns) collected. Increased flow speed resulted in both an increase in number of particles collected on the gill rakers and a smaller size distribution of particles collected (40-500 microns). Gill orientation did not affect filtering efficiency. These results suggest that the filtration mechanics of suspension feeding is closely linked to the both the animals swimming speed and the structural design of the buccal cavity and gill slits.