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22 <br />of those squawfish fortunate enough to have found a deep, permanent backwater. Valdez and <br />Cowdell's (1993) finding that catch rates decline less in deeper backwaters from fall to spring further <br />supports the importance of deep backwaters for overwinter survival. <br />The associated geomorphology studies (Rakowski and Schmidt, 1996) seem to have indicated that <br />high spring flushing flows have traditionally scoured out backwaters, increasing shoreline complexity <br />and available habitat. The spring flows for 1993 were above average and higher than any since 1984, <br />This was enough to flush the accumulated silt from backwater and other nursery habitat areas. <br />However, this flow did not have the desired effect of increasing habitat for the squawfish, as habitat <br />area overall decreased 50-75% in both sections. Clearly, all factors affecting the formation and <br />maintenance of nursery habitat are not understood. Increasing the relative quantity of deep persistent <br />habitats may increase survival of YOY squawfish, but the procedure for doing so is still unclear. <br />There is no clear correlation of total habitat availability or total SC habitat to either peak flow or <br />sampling flow. The observed effects are more closely associated with sampling year. The highest <br />quantity of habitat and second highest squawfish catch rates, occurred in 1992, prior to the high <br />spring flood of 1993. The high flows in 1995 again reduced the overall shoreline complexity, and <br />therefore backwater habitat. Subsequent years may reestablish that complexity (Rakowski and <br />Schmidt, 1996). <br />The high spring floods were expected to reduce non-native fish numbers. This did occur in the <br />higher peals years of `93 and `95, However, the decline in non-native catch rates was almost as great <br />over the winter period as over the flood period. In the lower peak years of `94 and `96, there was <br />a large increase in NNC numbers over the flood period, presumably due to earlier onset of NNC <br />reproduction in those years. In high water years, a "window of opportunity" could exist for <br />squawfish, to hatch and grow before large numbers ofNNCs again dominate their habitats. However, <br />