Rio Grande Silvery Minnow Fish Rescue 2022 Annual Report
Author(s): Archdeacon T.P., Boro M.E., Thomas L.I., Epping K.C.
Publication: Prepared by U.S. Fish and Wildlife Service, New Mexico Fish and Wildlife Conservation Office. Prepared for U.S. Bureau of Reclamation, Albuquerque Area Office, 73 p.
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 (YOY) based on their standard length.
During 2022, river drying began in June and the initial separation likely occurred between river kilometer (rkm) 240 and rkm 250 near the south boundary of Bosque del Apache National Wildlife Refuge. Between 5 June and 26 July 2022, we conducted rescue activities on 49.4 unique kilometers of main channel of the MRG that became intermittent. During rescue activities, we rescued 2,144 live RGSM. Of these, 824 were YOY RGSM, 364 were hatchery-reared RGSM, and 956 were unmarked RGSM (not all hatchery RGSM were marked during 2020 or 2021 releases). In addition, we found 182 dead RGSM during river intermittency. Spring run-off was low, though a greater number of YOY were collected in 2022 than in 2021. Overall, more fish were rescued in 2022 and wild adults and YOY made up the greatest proportions of RGSM caught, though not all hatchery fish were marked in 2021. Early spring runoff combined with extensive low flows may have contributed to fewer than expected numbers of adult RGSM encountered during fish rescue in 2022.