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-7- Average number of shad captured per standard tow in. Wahweap Bay was greater in 1977 than in 1976 (Table 1). Comparative samples for 1977 showed a 15-fold increase in shad numbers in August and a 7-fold increase in Septem- ber over values collected in 1976. Ccuparison of different lake areas in 1977 slowed shad numbers were of about the same magnitude at Wahweap and Bullfrog but considerably greater at Hite (Table 1). Peak densities of shad at Hite reached 461 per 1000 m3. Den- sities at Wahweap and Bullfrog peaked at 138 and 115 shad per 1000 m3, re- spectively. However, when results were plotted (Figure 3) trends at Bullfrog and Hite were similar despite differences in total numbers. Data showed a peak abundance in July as young-of-the-year shad became large enough to cap- ture in the trawl. wobers subsequently declined in August and rebounded in September, reaching a smaller secondary peak. Shad numbers at Wahweap fol- lowed the same general pattern, with the maim difference being a sharp decline in September. Average shad biemass per standard tow closely followed results of nunber of shad captured. At Bullfrog and Hite there were two distinct peaks in bio- mass with the higher September peak indicating growth. of shad with time (Fig- ure 4). Bicmass at Hite was consistently greater reaching a pear of 2276 g per tow. The biomass peak at Bullfrog was considerably less at 274 g per tow. A distinct.peak was not evident at Wahweap but remained quite constant at levels less than 100 g per tow. -Discussion most authors believe that threadfin shad spawn more than once a year. Kimsey (1958) and Kimsey et al. (1957) reported two major spawning Peaks for shad in California ponds in 1955 and in Lake Havasu, California-Arizona in 1956. Hida and Thcmpson (1962) found evidence which indicated shad spawned from June