Publication
Rio Grande Silvery Minnow Fish Rescue 2023 Annual Report
Date: 2023/12/21
Author(s): Archdeacon T.P., Thomas L.I., Dunnum P.M.
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, 20 p.
Abstract:
Rio Grande Silvery Minnow (RGSM) Hybognathus amarus are often trapped in isolated pools during of river drying from April 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 2023, river drying began in July 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 21 July and 31 August, we conducted rescue activities on 26.9 unique kilometers of main channel of the MRG that became intermittent. During rescue activities, we relocated 3,621 live RGSM. Of these, 3,530 were YOY RGSM, 85 were hatchery reared RGSM, and 6 were unmarked RGSM. In addition, we found 283 dead RGSM during river intermittency. Spring run-off was high, and more fish were rescued compared to years 2020-2022. Overall, more YOY fish were rescued in 2023 and wild YOY made up the greatest proportions of RGSM caught. However, the number of wild adults reflected poor recruitment over the previous three years and a population reliant on hatchery augmentation.