Technical Report

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


Date: 2024/01/01

Author(s): Archdeacon, T. P.

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


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.

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