An Evaluation of Three Artificial Structures to Reduce Predation on Hatchery-Reared Bonytail and Razorback Suckers

Authors: Kristopher Stahr

Year: 2018

Abstract

Bonytail, Gila elegans, and Razorback Sucker, Xyrauchen texanus, are two endangered fishes endemic to the Colorado River Basin. Population declines of both species are attributed to the introduction of non-native fish species and alteration to flow. Each year hatchery-reared Bonytail and Razorback Sucker are reintroduced back into the wild. However post-stocking survival is often poor as offspring are naïve to predation. Artificial structures have been discussed as a potential strategy to improve post-stocking survival but have yet to be evaluated. Therefore the objective of this study was to evaluate three different artificial structures to improve survival of hatchery-reared Bonytail and Razorback Sucker when exposed to predation. Three different structures (artificial macrophytes, large diameter vertical PVC, and small diameter horizontal PVC) and a control treatment (void of any structure) were used in the experiment. A repeated measures design experiment was conducted using Largemouth Bass, Micropterus salmoides, as a model predator and naïve hatchery-reared Bonytail and Razorback Suckers were used as prey. Experiments were conducted within one meter diameter circular tanks for one hour periods. Small diameter horizontal PVC and artificial macrophytes resulted in significantly higher survival for Bonytail compared to both the control treatment and large diameter vertical PVC. There was no significant difference in survival for Razorback Suckers between all treatments. Therefore it appears that artificial structure may play a larger role in post-stocking survival for Bonytail than Razorback Sucker, but future research is needed to confirm these results at a larger scale.