Publication
Rio Grande Silvery Minnow Fish Rescue 2021 Annual Report
Date: 2021/12/22
Author(s): Archdeacon T.P., Thomas L.I.
Publication: Prepared by U.S. Fish and Wildlife Service, New Mexico Fish and Wildlife Conservation Office. Prepared for U.S. Bureau of Reclamation, 19 p. DOI:10.13140/RG.2.2.26465.84326.
Abstract:
Rio Grande Silvery Minnow (RGSM) Hybognathus amarus are often trapped in isolated pools during times of river drying from June to October each year in the Middle Rio Grande (MRG) in New Mexico. Rescue of RGSM is performed by staff from the New Mexico Fish and Wildlife Conservation Office (NMFWCO) with assistance and coordination from several other agencies. Rio Grande Silvery Minnow are collected from isolated pools each day and transported on off-road utility vehicles equipped with water tanks and supplied with pure oxygen. Rescued RGSM are then transported and released into areas with continuous flows. Rescued RGSM are classified as either dead or alive, hatchery or wild origin, and adult or young-of-year based on their standard length.
During 2021 river drying began in June and the initial separation likely occurred between RM 74.0 and RM 67.0. Between 18 June and 26 August 2021, we conducted rescue activities on 38.7 unique miles of main channel of the MRG that became intermittent. Additionally, several miles were not rescued on Bosque del Apache National Wildlife Refuge due to dangerous driving conditions. During rescue activities, we rescued 818 live RGSM. Of these, 42 were young-of-year (YOY) RGSM, 271 were hatchery-reared RGSM, and 505 were unmarked RGSM (not all hatchery RGSM were marked during 2020). In addition, we found 51 dead RGSM during river intermittency. Spring run-off was low, resulting in few YOY in 2021. Combined with poor recruitment in 2020, the proportion of hatchery fish increased in 2021. Lack of spring runoff combined with extensive low flows may have contributed to lower than expected numbers of adult RGSM encountered during fish rescue in 2021.