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-12- high density shad population at Hite, in relation to.other lake areas, possibly inhibited a secondary spawn. Secondary ccanplements of eggs either failed to develop and/or latex developing younger females failed to produce a substantial secondary spawning peak. Numbers of shad captured correlated well with fish traces observed in the epilimnion on sonar echograms (Figures 5, 6, and 7). Traces became consistently mare numerous as the sampling season progressed. At Wahweap no traces were observed on the June 20 echograms, and no fish were captured in the trawl (Figure 5). On July 18 scattered traces were,observed, and 187 shad were captured per tow. During September echograns showed dense groupings of traces at all locations; however, trawl results were not consistently higher. It has been shown that as shad grow their ability to avoid capture in a trawl increases (Alfred Houser, personal catru iicaticn). Sonar echograms in August and September represented mostly juvenile and adult shad.. The adults were rarely captured, and juvenile catch decreased as size increased. Trawl catches were probably biased toward smaller individuals in late summer. However, decreased trawl catch in numbers and increased density of sonar fish traces may not be totally inconsistent. Fewer but larger fish may cause denser fish traces on sonar in cmparison to more numerous but smaller fish. Biomass was generally highest in September, while shad numbers were below previous peaks (Figures 3 and 4). Trawling depth may also have been a factor contributing to reduced catch in Septenber. Maximimi depth of the standard tow may not have been deep enough to sample fish in the 10-12 m range (35-40 ft) as shown by Comparative trawl samples for 1976 and 1977 showed a stronger year class of shad in Wahweap Bay (Table 1). Others have noticed relatively large differences in year class strength of shad (Bryant and Houser 1968,