Effects of Food Availability on Survival and Growth of Larval Razorback Suckers in Ponds

Abstract

Abstract The reasons for consistent failure of razorback sucker Xyrauchen texanus year-classes in Lake Mohave, Arizona–Nevada, are not entirely understood. To date, egg and larval predation by nonnative fishes is considered the most likely explanation, but food limitation may influence larval mortality. Our experiments in rearing razorback sucker larvae in ponds fertilized at three levels (“high,” “medium,” and “low”) with mean invertebrate densities of 43.3, 23.7, and 12.5 organisms/L, respectively, did not result in significant differences in larval survival (77.0, 89.8, and 67.4%, respectively). However, total larval growth was greater at the two higher invertebrate densities. Biovolume of food but not numbers of food organisms in guts increased linearly with growth of larvae. Numbers and biovolumes of food items did not differ relative to fertilization treatment. First foods of larval razorback suckers were diatoms, detritus, and algae, Soon thereafter, small rotifers and chironomids were taken, and l...