Success, Setbacks and Perseverance: Native Fish Conservation Efforts in the Blue River, Arizona 2012-2024

Authors: Brian Hickerson, Kent Mosher, Paul Reap, Betsy Grube

Year: 2024

Abstract

Projects to establish fish populations through translocation are commonly undertaken to conserve and recover imperiled native fishes and are often the highest priority tasks in recovery plans. Outcomes of translocation projects can often take years to determine and depend on stocking strategies employed, prevailing environmental conditions, and unforeseen circumstances. Importantly, success is rarely immediate and often requires active management over time. Native fish conservation efforts have taken place in the Blue River (Greenlee County, Arizona) since 2009. Efforts were initially focused on eradicating warmwater nonnative fishes from the lower 18 km of the river through barrier emplacement and mechanical removals, followed by translocation of three focal species: Spikedace Meda fulgida, Loach Minnow Tiaroga cobitis, and Roundtail Chub Gila robusta. Remarkable success was achieved by 2019 with the eradication of nonnative warmwater fishes, establishment of Spikedace and Roundtail Chub populations, and reestablishment of the Loach Minnow population. The success of translocation efforts in the lower Blue River led to translocation of Roundtail Chub and Spikedace to the middle Blue River (downstream of Blue, AZ) in 2017 and 2018 respectively. The outbreak of the Bringham Fire and Cow Canyon Fire within the Blue River watershed during the summer of 2020 prompted emergency salvage efforts of Spikedace and Roundtail Chub to the upper Blue River (upstream of Blue, AZ) out of concern of catastrophic post-fire effects to the lower and middle reaches of the river. Post-fire impacts on the lower and middle reaches of the river appeared to be mild during fall monitoring in 2020 likely due to well below average precipitation and discharge during the monsoon season. However, the continuation of well below average discharge (<10th percentile from 1999–2024) through July 2021 appeared to have suppressed native fish spawning success throughout the river. An above average monsoon season from July to September 2021 finally brought post-fire impacts (including flooding, debris flows, and sedimentation) throughout the middle and lower reaches of the river. As a result of both disturbances, the native fish populations crashed throughout the river. Below average winter and spring discharge in 2022 resulted in a second year of poor spawning conditions for native fish populations throughout the river. In addition, Spikedace failed to quickly rebound in the lower Blue River despite stocking in March, 2022. The well above average winter and spring discharge in 2023 coupled with stocking of Spikedace and Roundtail Chub in all three reaches of the river in February 2023, promoted strong year classes of native fish throughout the river, particularly for Spikedace in the middle and lower reaches. Loach Minnow struggled to respond as quickly as other species in the middle and lower reaches of the river, likely due to lingering sedimentation impacts on this sediment intolerant species. A similar pattern was seen in the lower river following impacts from the Bear Wallow Fire (2010) where Loach Minnow were the last of the native fish species to fully recover. Throughout all three river reaches, relative abundance of all three focal species across time was best explained by the interaction between the previous year’s relative abundance and various discharge metrics during the spring runoff period from January to April. The importance of discharge in determining population trends highlights that management actions, like translocation, are only effective as the subsequent hydrologic conditions allow for. Native fish establishment projects that plan for a single translocation followed by monitoring are not likely to be effective for many species give the increasingly extreme climactic conditions that desert fish in particular are exposed to. Managers should plan to be adaptive with their long term management approach, be ready to react to changing environmental conditions, and most importantly be prepared to patiently wait out setbacks in the short term to reach longer term success in the future.