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INTRODUCTION striped bass were stocked at Lake Powell in 1974 at a time when national interest in establishing this anadromous salt water species in fresh water impoundments was at its peak. state of the art knowledge at the time of stocking indicated that striped bass natural reproduction in freshwater systems was not common, and when it did occur it was not sufficient to provide a self- sustaining sport fishery in most cases. In retrospect, natural reproduction of striped bass was discovered in the lower Colorado River above Lake Havasu from 1966-1970 but was described by Edwards (1974) as limited and seemed to support the body of knowledge previously stated. Natural reproduction was discovered in Lake Mead, Arizona/Nevada in 1974 although that information was not immediately published (Allen and Rhoden, 1979). Following the best information available at time of introduction in 1974 it was thought that striped bass would have to be stocked to maintain a sport fishery and any natural reproduction that occurred would be a beneficial supplement. During the 1980's it was found that striped bass in Lake Powell and other Colorado River impoundments exist in a situation unique to any other location in the world where successful spawning of striped bass occurs in-lake as well as in the tributaries. The low organic load in the oligotrophic, deep canyon reservoirs allows oxygen to exist at the substrate level which is adequate to allow hatching of striped bass eggs that settle there (Gustaveson et al. 1984). Surface spawned semi- buoyant eggs descend at a rate of one foot per minute and hatch in 2-3 days. In most impoundments in the U. S. eggs not suspended by currents smother due to low oxygen levels. The average mature female striped bass is capable of spawning more than one million eggs. If an unusually high survival rate occurs from eggs to fingerling then striped bass populations are capable of extreme over population in any given year. 1