Meeting Abstract

P1.100  Thursday, Jan. 3  Particle filtering efficiency of a ram suspension-feeding fish WINTERS-MIST, E*; STROTHER, J/A; SUMMERS, A/P; Univ. of California, Irvine; Univ. of California, Irvine; Univ. of California, Irvine Mistyewp@yahoo.com

Recent work has suggested that many suspension-feeding fishes utilize cross-flow filtration to separate water from suspended food particles. According to this theory, water is siphoned out through the gill slits while food particles travel to the back of the oropharyngeal cavity without contacting or collecting on the gill rakers. While studies tracking the movement of particles in the oropharyngeal cavity seem to support this theory, the underlying mechanics of cross-flow filtration in fishes are not well understood. To examine how morphology and fluid dynamics affect filtering efficiency, we measured particle retention rates in a dynamically-scaled physical model of a fish head. This fish head was placed in a recirculating flow tank with water carrying neutrally-buoyant microspheres; sampling at the �esophagus� of the physical model was used to determine particle capture rates. We examined the affects of modifying the number, size, and permeability of the gill slits and characterized the effect of flow speed with each morphology. Unexpectedly, while particle capture rates tended to increase with swimming speed this relationship exhibited strong non-linearity. Also, at higher swimming speeds larger vortices were observed within the oral cavity that decreased flow through the oral tract and even ejected particles that had already entered the mouth. This addition of vortices may limit the maximum speed at which efficient particle filtration can occur.