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16 <br />Arizona Bay Backwater <br />On 4 April 1985, a rising lake level (elevation 196.80 m [645.67']) <br />combined with wave action driven by strong westerly winds caused a small <br />breach between Lake Mohave and the Arizona Bay backwater. As bhe lake <br />continued to rise to a maximum of 197.02 m, the entire berm became <br />submerged to a depth of ca. 0.25 m, and numerous fishes, including green <br />sunfish, bluegill, threadfin shad, channel catfish, largemouth bass and <br />common carp invaded the backwater. This occurred at a time when <br />razorback sucker in the backwater were abundant and relatively large in <br />size (Fig. 5). <br />Experimental gill nets were deployed for 24 hr on 15 April to <br />collect recently arrived fishes for food habit analysis. Nets were <br />examined At intervals of not less than 2 hrs to insure sucker larvae, if <br />eaten, would be identifiable and quantifiable. Each specimen removed <br />from the nets was injected in the body cavity with 10% formalin to halt <br />digestion, then preserved intact. Five separate instances of green <br />sunfish attacking and eating sucker larvae were observed during the <br />netting period. Five fish species were collected. Only green sunfish <br />had consumed sucker larvae, more than a third of which each contained an <br />average of 3.9 larvae (Table 5). <br />The backwater remained confluent with Lake Mohave until 5 May, when <br />lake elevation dropped to 196.60 m. By that time, bluegill, green <br />sunfish and threadfin shad were abundant and razorback sucker could no <br />longer be collected. While sucker larvae may have emmigrated just as <br />other species immigrated, no such activity was seen and we attribute the <br />decline at least in part to predation. When reclaimed a second time in <br />October 1986, only introduced species were in the backwater; razorback <br />sucker adults or young were not taken.