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5 <br />Substrates are largely coarse gravel around margins and organic silts in <br />deeper parts. Shallow regions are occupied by dense stands of <br />water-milfoil (Myriophyllum spicatum) interspersed with curly leaf <br />pondweed (Potamogeton crispus). Fishes which initially inhabited the <br />backwater were threadfin shad (Dorosoma petenense), carp (Cyprinus <br />carpio), channel catfish (Ictalurus punctatus), mosquitofish (Gambusia <br />affinis), largemouth bass (Micropterus salmoides), green sunfish <br />(Le omis cyanellus), and bluegill (Lepomis macrochirus). These were <br />removed by ichthyocide in autumn 1984, and the backwater stocked in <br />January 1985 with adult razorback suckers (30 female, 150 male) <br />collected from Arizona Bay. These spawned successfully and produced <br />larvae, which were monitored through their disappearance after breaching <br />of the berm in early April 1985 (see below). <br />SPAWNING ACTIVITY <br />Razorback sucker spawning was first observed 8 January 1985 along <br />Arizona Bay shorelines (Table 1) in the same general habitat described <br />by Mueller et al. (1982). Water temperature was 11.50C. Numbers often <br />were difficult to accurately assess because of surface conditions, but <br />more than 1000 individuals were observed on days of optimum viewing. <br />Spawning acts (described by Douglas 1952 and Minckley 1983) were <br />repeatedly witnessed. On several occasions, the area was monitored <br />. continuously for 24 hour periods and no diel pattern of reproductive <br />activity could be identified. Surface conditions produced by waves <br />higher than ca. 25 cm were usually accompanied by cessation of spawning, <br />at least in shallow, near-shore areas, and thus appeared a more <br />important determinant of activity than time of day.