Fish aid — the lake mead fertilization project

Sport fishing at Lake Mead in Nevada and Arizona is a resource valued at neariy $100 million per year to southern Nevada. During the past two decades, saimonids, mostly trout, have disappeared entirely, the largemouth bass catch has drasticaliy declined despite greater fishing pressure, and the condition factors for striped bass have steadily deteriorated. It appears that a major reduction in phosphorus loading caused by the upstream impoundment of the Colorado River to form Lake Powell in 1963 and advanced wastewater treatment removal of phosphorus from domestic wastewater inflows in 1981 are the principal factors responsible for decreased production at all levels of the food chain. The Lake Mead Fertilization Project is an attempt to reverse these declining fisheries. The first large-scale test of fertilization occurred on May 30, 1987. More than 300 boats and 1,000 volunteers helped spread 20,000 gallons (75.7 m³) of liquid ammonium polyphosphate over 19,000 acres (7700 ha) of lake surface. Highlights of the history of the project and initial results, which indicate that the test was extremely successful, are discussed.