Predicted Native Fish Response, Potential Rewards and Risks from Flow Alteration in a New Mexico Arid Mountain Stream

Abstract

AbstractWater and natural resource managers are concerned with evaluating how fish habitat and populations may respond to water diversions and small‐scale flow augmentations. We used two‐dimensional hydraulic models, habitat suitability curves and an individual‐based population viability model to assess whether flow augmentations of about 0.28–0.57 m3/s would create suitable habitat for federally listed native fish loach minnow Rhinichthys cobitis and spikedace Meda fulgida in a reach of the Gila River, New Mexico, and then examined how fish population viability may change under a variety of colonization and extinction scenarios. These simulations help to inform water management decisions in a reach of the Gila River where river diversions currently exist and new diversions and augmentations are being proposed. Our results suggest that the flow augmentations evaluated will result in small changes (on average across life stages, −0.22% to 4.06%) in suitable habitat for loach minnow and spikedace depending on augmentation scenario and fish life stage. While these percent changes are small, they would result in a reduction in the dewatering of the river channel in a river reach where native fish abundance is thought to be low. Actual native fish responses to these habitat changes are unknown; however, these flow augmentations could potentially allow these native species to re‐colonize this river segment from upstream or downstream sources increasing species distribution and likely population viability. Maintaining viable populations of native fish in this river reach is dependent on complex factors including persistence of suitable habitat for multiple life stages, connectivity with other populations and minimizing risk of invasion from non‐native species. We recommend that these predictions from the habitat and population models be tested and verified in an adaptive management framework linking modelling, experimental management, monitoring and reassessment to inform water management decisions in the Gila River. Copyright © 2017 John Wiley & Sons, Ltd.