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measured by fall gill net catches (Figure 4). The population peak represented that year was similar to many similar peaks over the past decade. As forage declined in 1997 and collapsed in 1998 the year class began to lessen in number. Striped bass abundance peaks during and/or after a shad peak (Figure 5). The population crashes after the peak and then builds for 3 to 4 years to the next peak and subsequent crash. Numbers do not necessarily correlate to fish size as old fish may still be less than 20 inches during periods of shad shortage. During the past 5 years striped bass abundance has shown the lowest variability since sampling began. SPAWNING, MIGRATION AND MOVEMENTS Spawning Movements Striped bass are anadromous spawners historically and exhibit strong migrational tendencies in fresh water (Setzler et al. 1980). Mature fish spawn in or below Cataract Canyon, a 19 km-Iong Colorado River gorge containing 23 major rapids, which is approximately 32 km above Lake Powell's headwaters. Turbulent conditions preferred by spawning striped bass are provided by the series of rapids. No mature adult striped bass have been collected above Cataract Canyon (Persons et al. 1981; Persons and Bulkley 1982). Occasionally, juvenile striped bass which can withstand warmer temperatures have been collected above the rapids during low flow periods in the summer (Valdez 1990). Warm summertime temperatures and high turbidity make year-round striped bass occupation of the river infrequent and unlikely. Two other major tributaries, San Juan and Escalante Rivers, are small in comparison to the Colorado and spawning striped bass migrations have never been reported. However, there have been occasions when large schools of prespawning adults have been found in the lake headwaters near the inflow of both rivers. In most years since 1979 there has been a prespawning 27