Predation by odonate nymphs on larval razorback suckers (Xyrauchen texanus) under laboratory conditions
High larval mortality has plagued efforts to raise razorback suckers ( Xyrauchen texanus ) in a Lake Mohave, Arizona-Nevada backwater. Observations indicate odonate nymph densities may be high enough to impact larval survival. In laboratory tests conducted in aquaria, damselfly (Coenagrionidae: Enallagma sp.) and dragonfly (Libellulidae: Tramea sp.) nymphs consumed 81% and 76% respectively of 11.8 ± 0.7 mm total length larval razorbacks in 7 days compared to 12% mortality in controls. Larger razorback larvae (14 to 15 mm TL) were less susceptible than smaller fish, showing 53% mortality versus 18% in controls. Extensive growth of sago pondweed ( Potamogeton pectinatus ) may exacerbate predation effects in the backwater, by allowing odonates access to more of the water column.