Degree Awarded: M.S. Biology. American University There is high mortality during the early life stages of many fish species. The ability of larvae to overcome this mortality is key to survival and study of factors that affect mortality is ecologically and commercially significant. If food is not available during this early stage, larvae will reach a point at which they are no longer able to feed even when food becomes available, known as the Point of No Return (PNR). Past studies on PNR have been used to predict fish yields in hatcheries and are conducted on commercially valuable fish. Zebrafish (Danio rerio) are a more ecologically relevant model organism. By delaying the onset of feeding in zebrafish, we can determine their PNR. Results indicate that the PNR in zebrafish is at 9 days post fertilization and that observations of conspecifics is important for the acquisition of feeding behavior.