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M <br />h? <br />p <br />N <br />8 <br />Growth in the Yuma Cove backwater substantially exceeded that <br />obtained for razorback suckers under hatchery conditions (FWS <br />files, Dexter NFH), and was about twice that attained in central <br />Arizona urban lakes and elsewhere (Marsh 1990). This exceptional <br />growth may in part have been enhanced by a stochastic event. A <br />flash flood on 10 August discharged a visibly large quantity of <br />organic material, including abundant feral burrow (Equus asinus) <br />faeces, into the backwater (Burke and Horn, personal obs&rvations), <br />which undoubtedly contributed significantly to the nutrient budget <br />of the system. That influx of nutrients would have stimulated <br />r <br />primary productivity, which in turn enhanced secondary production <br />of zooplankters and benthic invertebrates. Thus, food resources <br />for young razorback suckers would have been enhanced, and could <br />have resulted in the observed growth rates. <br />At least five ripe males were among the group of fish removed from <br />the Yuma Cove backwater in November; sexually maturity thus had <br />been attained by nine months of age. Prior to this observation the <br />earliest age at maturation for males was two years, as reported, for <br />some individuals at Dexter NFH and in central Arizona ponds (FWS <br />files, Marsh 1990, Minckley et al. 1991). <br />?J