Fine sediment affects on survival to emergence of robust redhorse |
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Authors: | Cecil A Jennings Erik W Dilts Jr" target="_blank">James L SheltonJr Rebecca Cull Peterson |
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Institution: | (1) U. S. Geological Survey, Georgia Cooperative Fish and Wildlife Research Unit, D.B. Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA 30602, USA;(2) Present address: CenterPoint Energy, 525 Milam Street, Shreveport, LA 71101, USA;(3) D. B. Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA 30602, USA;(4) Georgia Cooperative Fish and Wildlife Research Unit, D. B. Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA 30602, USA |
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Abstract: | Robust redhorse (Moxostoma robustum) is a rare riverine sucker for which life history information is scarce. Spawning occurs over loose gravel substrate and
eggs and larvae may be adversely affected by fine sediments among the gravel. A 2-year study was conducted to determine the
threshold at which fine sediments are detrimental to successful egg incubation and larval emergence. Year 1 gravel treatments
contained 0, 25, 50, and 75% fine sediments. Mean survival during Year 1 ranged from 63.5% in the 0% fine sediment treatment
to 0% in the 75% fine sediment treatment. The results also indicated an adverse affect threshold between 0 and 25% fine sediment.
Year 2 gravel treatments contained 0, 5, 10, 15, 20, and 25% fine sediments. Mean survival during Year 2 ranged from 69.8%
in the 0% treatment to 9.1% in the 25% treatment. Year 2 results also identified the 15% fine sediment treatment as the threshold
at which survival began to decline. Substrates at one known spawning area used by robust redhorse typically contain 25 to
50% fine sediment, but the spawning act cleans some fines from the egg pocket. Whether the “cleaning” that results from the
spawning act reduces the fines sufficiently to avoid adverse effects is unknown. According to our results, survival rates
of robust redhorse eggs and larvae are predicted to be about 8.0% or less when fine sediment is >25%. |
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