Lower lethal temperature of the endangered Rio Grande silvery minnow and its implications for propagation and reintroduction

ABSTRACT

The lower lethal temperature of the endangered Rio Grande silvery minnow, Hybognathus amarus, was estimated from survival rates of fish overwintered in above-ground tanks. Temperature went to 0.0°C both winters. In 2012–2013, survival of Age class 0 fish was 79.87%, and in 2013–2014, survival of Age class 1 fish was 97.1%, suggesting that if Rio Grande silvery minnow is subjected to seasonal temperature changes, lower lethal temperature is ≤0.0°C. Results show that heating hatchery water in the winter is unnecessary. Additionally, current management guidelines that preclude reintroduction of the species into river sections where winter temperatures are ≤1°C must be reevaluated.

KEYWORDS:

• Endangered species
• Hybognathus amarus
• temperature guideline for culture and reintroduction

Acknowledgments

We thank Page Pegram, Grace Haggerty, and Linda Tenorio for assistance in the field. We thank Ken Ferjancic (HDR, Inc.), Dave Ward (HDR, Inc.), Justin K. Reale, Ariane Pinson, and Grace Haggerty for reviewing the manuscript. Fish were cultured under USFWS Permit TE169770-5 and New Mexico Department of Game and Fish Permit 3417.

Funding

Funds for operations and maintenance of the Los Lunas Silvery Minnow Refugium are provided by Grant Agreement No. 08–FG–40–2803 from the U.S. Bureau of Reclamation. Funds for monitoring at the Rio Grande Nature Center are provided by the U.S. Army Corps of Engineers Middle Rio Grande Species Collaborative Program Authority.

Additional information

Funding

Funds for operations and maintenance of the Los Lunas Silvery Minnow Refugium are provided by Grant Agreement No. 08–FG–40–2803 from the U.S. Bureau of Reclamation. Funds for monitoring at the Rio Grande Nature Center are provided by the U.S. Army Corps of Engineers Middle Rio Grande Species Collaborative Program Authority.