Approaches for re-establishing Bonytail, Gila elegans populations within the Colorado River basin

Authors: Ron* Kegerries, Brandon Albrecht, Mark McKinstry, Dave Speas

Year: 2015 (xlvii)

Abstract

Bonytail, Gila elegans, is one of four endangered fish species in both the upper and lower Colorado River basins. To date, there has been no measurable success in recovering, or developing stable populations of this fish species anywhere in the Colorado River basin outside of hatchery or predator-free, pond-type settings. Since 1996, nearly 250,000 Bonytail have been stocked into the upper Colorado River basin, mostly within the Green and Colorado rivers (approximately 90%). Despite these stocking efforts less than 10,000 (<4%) individuals have been captured or detected via various sampling methods. According to capture history data, only 34 individual Bonytail were at large for more than a year before being recaptured. The longest period between captures was 7 years: a single fish stocked into the Colorado River in 2007. Due to the poor survival and recruitment under the current stocking plan, the U.S. Bureau of Reclamation supported the development of different approaches for conserving and recovering Bonytail with emphasis on all life stages to promote recruitment. Biologists from the upper and lower Colorado River basins discussed research-based approaches that may be beneficial to increase survival and recruitment of the species. The two primary approaches included: 1) releasing Bonytail into complex off-channel wetlands within the Green River, and 2) releasing Bonytail into coves within Lake Powell that provide turbidity and cover near the Colorado inflow. The goal for each would be to establish populations that reproduce in areas that contain habitat necessary for rearing, growth, and potentially recruitment. Life-history strategies of Bonytail that provide advantages to improve survival and recruitment include prolific spawning, non-specificity of spawning substrates, and lentic spawning. Under each of these approaches stocked fish would be tracked, reproduction assessed, and recruitment measured through continued monitoring. These approaches are aimed at improving recovery potential, while generating ideas and cooperation among the cooperators who work with Bonytail.