Abstract: A method for administering compounds, including proteins, non-protein drugs, and nucleic acids, to aquatic animals, especially fish, in an aquatic medium wherein the compound is added to the medium and ultrasound is applied to the medium to enhance or effect the uptake of the compound by the animal. In one example, gonadotropin-releasing hormone analogue (GnRHa) was administered to fish via water to which ultrasound was applied for ten to fifteen minutes at an intensity of 1.7 W/cm.sup.2. Fish treated with ultrasound had blood levels of 3.29.+-.1.0 ng/ml of GnRHa as compared to levels of 0.50.+-.0.23 ng/ml for fish exposed to GnRHa in the absence of ultrasound.