Technical Report

Rio Grande Silvery Minnow Augmentation in the Middle Rio Grande, New Mexico, Annual Report 2023

URL: https://webapps.usgs.gov/mrgescp/documents/2023-Annual-augmentation-Report-FINAL.pdf

Date: 2024/01/01

Author(s): Archdeacon, T. P.

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

Abstract:

This report covers New Mexico Fish and Wildlife Conservation Office (NMFWCO) 114 Rio Grande Silvery Minnow (RGSM) augmentation activities for the 2023 cohort.

• Spring runoff in early 2023 was high, resulting in a request of 60,000 hatchery-reared age-0 fish to supplement the wild 2023 cohort.

• The color of visible implant elastomer (VIE) tags used for identifying RGSM released in 2023 was red right dorsal for all facilities.

• Based on September 2023 population monitoring, the Middle Rio Grande valley had > 1.0 RGSM per 100m² but <50% occupied sites in the San Acacia Reach, leading to a final request of 46,000 RGSM for release in the San Acacia Reach.

• 46,484 hatchery-reared age-0 Rio Grande Silvery Minnows were released in November and December 2023. All were given a red right VIE tag prior to release.

• Fish from the Los Lunas Silvery Minnow Refugium did not meet minimum condition factor requirements and were held back to grow out to a larger size.

• 120 VIE-marked fish were recaptured between January and December 2023, all from the 2023 cohort. The majority of recaptures (N = 85) were during fish rescue activities.

• A pilot mark-recapture study continued in 2023 to determine the feasibility of robust-design mark recapture to estimate monthly survival, movement, and capture efficiency of Rio Grande Silvery Minnow. A total of 3,983 Rio Grande Silvery Minnow were captured in 2023, compared to 7 in 2022.