Annual Report

Rio Grande Silvery Minnow Fish Rescue 2024 Annual Report

URL: https://webapps.usgs.gov/mrgescp/documents/Thomas-et-al_2025_Fish-Rescue-Annual-Report-2024-Final.pdf

Date: 2025/02/10

Author(s): Thomas L.I., Archdeacon T.P., Dunnum P.M.

Publication: U.S. Fish and Wildlife Service report submitted to U.S. Bureau of Reclamation

Abstract:

Rio Grande Silvery Minnow (Hybognathus amarus; hereafter RGSM) are often trapped in isolated pools during river drying from April to October each year in the Middle Rio Grande (MRG) of New Mexico. Rescue of RGSM is performed by staff from the New Mexico Fish and Wildlife Conservation Office (New Mexico FWCO) 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 2024, 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 15 July and 21 August, we conducted rescue activities on 22.5 unique kilometers of main channel of the MRG that became intermittent. During rescue activities, we relocated 2,250 live RGSM. Of these, 1,027 were YOY RGSM, 111 were hatchery reared RGSM, and 1,112 were wild RGSM. In addition, we found 340 dead RGSM during river intermittency. Spring run-off was average, and more fish were rescued compared to years 2020-2022, but there were fewer than in 2023. Overall, more adult fish were rescued in 2024 and wild adults made up the greatest proportions of RGSM caught. However, the number of YOY reflected poor recruitment during 2024.