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6 <br />TABLE 1. Chronology of observed razorback sucker reproduction in <br />Arizona Bay, Hammerhead Cove, and the Arizona Bay backwater, <br />Lake Mohave, Arizona-Nevada, 1985. <br /> Arizona Bay Hammerhead Cove Arizona Bay Backwater <br />First Spawning 8 January 15 January unobserved <br />First Larvae 17 February 9 February 7 March <br />Last Spawning 1 May 26 January- unobserved <br />Last Larvae 26 April 3 April 27 April <br />Spawning began a week later on 15 January in Hammerhead Cove (Table <br />1), where numbers were far fewer (20-30 adults) than Arizona Bay. While <br />spawning in Arizona Bay occurs within about 1000 m2 of shoreline <br />(Mueller et al. 1982), Hammerhead Cove provides at most a tenth that <br />amount of suitable area. Per unit area density thus was similar in both <br />areas, and total numbers appeared to reflect available spawning habitat. <br />On 21-24 February, shorelind from Arizona Bay to Davis Dam (Fig. 1) <br />were inspected during calm, daylight periods for concentrations of adult <br />suckers. Scattered individuals were observed in many locations, but <br />aggregations were only in Six Mile Area, Nine Mile Coves, and Arizona <br />Bay. Bozek et al. (1984) reported similar observations, although we saw <br />fewer suckers in the first two places. Suckers lake wide were near <br />bottom at depths ranging from <1 to ca. 5 m; most were in <2 m of water. <br />Most fish were over coarse gravel or rubble substrates; occasional <br />individuals were over bedrock, silt, aquatic macrophytes, or submerged <br />riparian vegetation. Common carp (Cyprinus carpio), threadfin shad <br />(Dorosoma petenense) and rainbow trout (Salmo gairdneri) were abundant <br />in trammel and beach seine samples from sucker spawning areas in Arizona <br />Bay and Hammerhead Cove. Except for carp fishes, these were rarely <br />observed.