Experimental assessment of variable flows on growth and survival
September 1998 - April 2001
- Patuxent Wildlife Research Center
In this study, we investigated the effects of pulsed, high-velocity water flow on the eggs and larvae of robust redhorse M. robustum and V-lip redhorse M. collapsum in three separate experiments that lasted from 21 to 38 d after egg fertilization. Hatch sucess and length at 24 h posthatch were quantified for eggs and larvae to discern any effects before larvae emerged from nests. Final length (of surviving larvae) and larval survival were quantified at the end of experimental periods to discern any effects after larvae emerged from nests. The research suppors the hypothesis that pulsed, high-velocity water flow can affect some aspects of catostomid early life development. Catostomid suckers are a diverse group of fishes endemic to most streams and rivers in the south-eastern United States. Reproduction occurs during late spring when water temperatures begin to rise. Water releases from hydropower-generating dams often occur in the spring as energy demand for cooling increases. These water releases increase the frequency of both high-velocity and low-velocity flow pulses while reducing their duration. Because of the low abundance of robust redhorses and other species of catastomids across thir historic ranges, special attention should be given to understanding the biological and physical conditions necessary for successful reproduction. Extended low-velocity flow periods are natural occurrences in low-rainfall years, and at least two species of catastomids (i.e., robust and V-lip red horse) might benefit from longer periods of stable low-velocity water flow during the spring spawning season. A return to natural flow patterns in dam-regulated rivers could help increase early larval survival and restore populations downstream from dams to their predam densities.